Localize strings related to CI validation

This change adds translations for missing strings in the blob viewer
related to CI YAML validation.

app/views/projects/blob/viewers/_gitlab_ci_yml.html.haml

 - if viewer.valid?(project: @project, sha: @commit.sha, user: @current_user)
   = sprite_icon('check')
-  This GitLab CI configuration is valid.
+  = s_('Pipelines|This GitLab CI configuration is valid.')
 - else
   = sprite_icon('warning-solid')
-  This GitLab CI configuration is invalid:
+  = s_('Pipelines|This GitLab CI configuration is invalid:')
   = viewer.validation_message(project: @project, sha: @commit.sha, user: @current_user)
 
-= link_to 'Learn more', help_page_path('ci/yaml/README')
+= link_to _('Learn more'), help_page_path('ci/yaml/README')

app/views/projects/blob/viewers/_gitlab_ci_yml_loading.html.haml

 = loading_icon(css_class: "gl-vertical-align-text-bottom mr-1")
-Validating GitLab CI configuration…
+= s_('Pipelines|Validating GitLab CI configuration…')
 
-= link_to 'Learn more', help_page_path('ci/yaml/README')
+= link_to _('Learn more'), help_page_path('ci/yaml/README')

locale/gitlab.pot

@@ -20563,6 +20563,12 @@ msgstr ""
 msgid "Pipelines|There was an error fetching the pipelines. Try again in a few moments or contact your support team."
 msgstr ""
 
+msgid "Pipelines|This GitLab CI configuration is invalid:"
+msgstr ""
+
+msgid "Pipelines|This GitLab CI configuration is valid."
+msgstr ""
+
 msgid "Pipelines|This is a child pipeline within the parent pipeline"
 msgstr ""
 
@@ -20578,6 +20584,9 @@ msgstr ""
 msgid "Pipelines|Trigger user has insufficient permissions to project"
 msgstr ""
 
+msgid "Pipelines|Validating GitLab CI configuration…"
+msgstr ""
+
 msgid "Pipelines|Visualize"
 msgstr ""