Migrate project form group to use PJ style classes

Remove the bootstrap style class and replace it with PJ compliant style
classes.

app/assets/javascripts/confidential_merge_request/components/project_form_group.vue

@@ -120,7 +120,7 @@ export default {
         :selected-project="selectedProject"
         @click="selectProject"
       />
-      <p class="text-muted mt-1 mb-0">
+      <p class="gl-text-gray-600 gl-mt-1 gl-mb-0">
         <template v-if="projects.length">
           {{ $options.i18n.privateForkSelected }}
         </template>
@@ -134,7 +134,7 @@ export default {
         </template>
         <gl-link
           :href="helpPagePath"
-          class="w-auto p-0 d-inline-block text-primary bg-transparent"
+          class="gl-w-auto gl-p-0 gl-display-inline-block gl-bg-transparent"
           target="_blank"
         >
           <span class="sr-only">{{ $options.i18n.readMore }}</span>

spec/frontend/confidential_merge_request/components/__snapshots__/project_form_group_spec.js.snap

@@ -12,7 +12,7 @@ exports[`Confidential merge request project form group component renders empty s
     <!---->
      
     <p
-      class="text-muted mt-1 mb-0"
+      class="gl-text-gray-600 gl-mt-1 gl-mb-0"
     >
       
         No forks are available to you.
@@ -27,7 +27,7 @@ exports[`Confidential merge request project form group component renders empty s
       </a>
        and set the fork's visibility to private. 
       <gl-link-stub
-        class="w-auto p-0 d-inline-block text-primary bg-transparent"
+        class="gl-w-auto gl-p-0 gl-display-inline-block gl-bg-transparent"
         href="/help"
         target="_blank"
       >
@@ -62,13 +62,13 @@ exports[`Confidential merge request project form group component renders fork dr
     />
      
     <p
-      class="text-muted mt-1 mb-0"
+      class="gl-text-gray-600 gl-mt-1 gl-mb-0"
     >
       
         To protect this issue's confidentiality, a private fork of this project was selected.
        
       <gl-link-stub
-        class="w-auto p-0 d-inline-block text-primary bg-transparent"
+        class="gl-w-auto gl-p-0 gl-display-inline-block gl-bg-transparent"
         href="/help"
         target="_blank"
       >