Update other instances to `RSpec.describe` in development docs

The following discussion from !33695 (merged) should be addressed:

• @splattael started a discussion:

  Non-blocking:

  Should we also update other references of describe X do in our docs as well?

  • describe API::Labels do
  • describe API::Labels do
  • describe Geo::WidgetReplicator do
  • describe Resolvers::Geo::WidgetRegistriesResolver do
  • describe Geo::WidgetRegistryFinder do
  • describe GitlabSchema.types['WidgetRegistry'] do
  • describe "#==" do
  • describe MigratePipelineStages do
  • describe 'Login' do
  • describe 'Login' do
  • describe 'Login' do
  • describe 'Login' do
  • describe 'Login' do
  • describe 'Issues' do
  • describe 'Issue' do

  Moreover, looking at https://docs.gitlab.com/ee/development/testing_guide/end_to_end/beginners_guide.html#create-a-skeleton-test I assume we should also update to RSpec.context X do? A genuine question. 🤷