Improve build status specs contexts descriptions

app/views/ci/status/_badge.html.haml

+- status = local_assigns.fetch(:status)
+
 - if status.has_details?
   = link_to status.details_path, class: "ci-status ci-#{status}" do
     = custom_icon(status.icon)

spec/lib/gitlab/ci/status/build/cancelable_spec.rb

@@ -65,7 +65,7 @@ describe Gitlab::Ci::Status::Build::Cancelable do
   describe '.matches?' do
     subject { described_class.matches?(build, user) }
-    context 'build is cancelable' do
+    context 'when build is cancelable' do
       let(:build) do
         create(:ci_build, :running)
       end

spec/lib/gitlab/ci/status/build/play_spec.rb

@@ -51,7 +51,7 @@ describe Gitlab::Ci::Status::Build::Play do
   describe '.matches?' do
     subject { described_class.matches?(build, user) }
-    context 'build is playable' do
+    context 'when build is playable' do
       context 'when build stops an environment' do
         let(:build) do
           create(:ci_build, :playable, :teardown_environment)

spec/lib/gitlab/ci/status/build/retryable_spec.rb

@@ -65,7 +65,7 @@ describe Gitlab::Ci::Status::Build::Retryable do
   describe '.matches?' do
     subject { described_class.matches?(build, user) }
-    context 'build is retryable' do
+    context 'when build is retryable' do
       let(:build) do
         create(:ci_build, :success)
       end

spec/lib/gitlab/ci/status/build/stop_spec.rb

@@ -53,7 +53,7 @@ describe Gitlab::Ci::Status::Build::Stop do
   describe '.matches?' do
     subject { described_class.matches?(build, user) }
-    context 'build is playable' do
+    context 'when build is playable' do
       context 'when build stops an environment' do
         let(:build) do
           create(:ci_build, :playable, :teardown_environment)