refactor(gb)!: remove obsolete `gb` plugin (#11115)

plugins/gb/README.md

-# `gb` plugin
-
-> A project based build tool for the Go programming language.
-
-See https://getgb.io for the full `gb` documentation
-
-* * * *
-
-- Adds completion support for all `gb` commands.
-- Also supports completion for the [`gb-vendor` plugin](https://godoc.org/github.com/constabulary/gb/cmd/gb-vendor).
-
-To use it, add `gb` to your plugins array:
-```sh
-plugins=(... gb)
-```
-
-## Caveats
-
-The `git` plugin defines an alias `gb` that usually conflicts with the `gb` program.
-If you're having trouble with it, remove it by adding `unalias gb` at the end of your
-zshrc file.

plugins/gb/_gb

-#compdef gb
-#autoload
-
-_gb () {
-	local ret=1 state
-	_arguments -C ':command:->command' '*::options:->options' && ret=0
-
-	case $state in
-	(command)
-		local -a subcommands
-		subcommands=(
-			"build:build a package"
-			"doc:show documentation for a package or symbol"
-			"env:print project environment variables"
-			"generate:generate Go files by processing source"
-			"help:displays the help"
-			"info:info returns information about this project"
-			"list:list the packages named by the importpaths"
-			"test:test packages"
-			"vendor:manage your vendored dependencies"
-		)
-		_describe -t subcommands 'gb subcommands' subcommands && ret=0
-		;;
-	(options)
-		case $line[1] in
-		(build)
-			_arguments \
-				-f'[ignore cached packages]' \
-				-F'[do not cache packages]' \
-				-q'[decreases verbosity]' \
-				-P'[the number of build jobs to run in parallel]' \
-				-R'[sets the base of the project root search path]' \
-				-dotfile'[output a dot formatted file of the build steps]' \
-				-ldflags'["flag list" arguments to pass to the linker]' \
-				-gcflags'["arg list" arguments to pass to the compiler]' \
-				-race'[enable data race detection]' \
-				-tags'["tag list" additional build tags]'
-			;;
-		(list)
-			_arguments \
-				-f'[alternate format for the list, using the syntax of package template]' \
-				-s'[read format template from STDIN]' \
-				-json'[prints output in structured JSON format]'
-			;;
-		(test)
-			_arguments \
-				-v'[print output from test subprocess]' \
-				-ldflags'["flag list" arguments to pass to the linker]' \
-				-gcflags'["arg list" arguments to pass to the compiler]' \
-				-race'[enable data race detection]' \
-				-tags'["tag list" additional build tags]'
-			;;
-		(vendor)
-			_gb-vendor
-		esac
-		;;
-	esac
-
-	return ret
-}
-
-_gb-vendor () {
-	local curcontext="$curcontext" state line
-	_arguments -C ':command:->command' '*::options:->options'
-
-	case $state in
-	(command)
-		local -a subcommands
-		subcommands=(
-			'delete:deletes a local dependency'
-			'fetch:fetch a remote dependency'
-			'list:lists dependencies, one per line'
-			'purge:remove all unreferenced dependencies'
-			'restore:restore dependencies from the manifest'
-			'update:update a local dependency'
-		)
-		_describe -t subcommands 'gb vendor subcommands' subcommands && ret=0
-		;;
-	(options)
-		case $line[1] in
-			(delete)
-				_arguments \
-					-all'[remove all dependencies]'
-				;;
-			(fetch)
-				_arguments \
-					-branch'[fetch from a particular branch]' \
-					-no-recurse'[do not fetch recursively]' \
-					-tag'[fetch the specified tag]' \
-					-revision'[fetch the specific revision from the branch (if supplied)]' \
-					-precaire'[allow the use of insecure protocols]' \
-				;;
-			(list)
-				_arguments \
-					-f'[controls the template used for printing each manifest entry]'
-				;;
-			(restore)
-				_arguments \
-					-precaire'[allow the use of insecure protocols]'
-				;;
-			(update)
-				_arguments \
-					-all'[update all dependencies in the manifest or supply a given dependency]' \
-					-precaire'[allow the use of insecure protocols]'
-				;;
-		esac
-		;;
-	esac
-}
-
-_gb