Merge branch 'bvl-only-require-po-parser-in-rake' into 'master'

Only require `simple_po_parser` in rake task that needs it

Closes #37379

See merge request !14018

lib/gitlab/i18n/po_linter.rb

-require 'simple_po_parser'
-
 module Gitlab
   module I18n
     class PoLinter

lib/tasks/gettext.rake

 require "gettext_i18n_rails/tasks"
+require 'simple_po_parser'
 
 namespace :gettext do
   # Customize list of translatable files

spec/lib/gitlab/i18n/po_linter_spec.rb

 require 'spec_helper'
+require 'simple_po_parser'
 
 describe Gitlab::I18n::PoLinter do
   let(:linter) { described_class.new(po_path) }