Replacing bootstrap utilities with gl-*

As per maintainer's review

app/assets/javascripts/snippets/components/show.vue

@@ -35,7 +35,7 @@ export default {
     <template v-else>
       <snippet-header :snippet="snippet" />
       <snippet-title :snippet="snippet" />
-      <blob-embeddable v-if="embeddable" class="mb-3" :url="snippet.webUrl" />
+      <blob-embeddable v-if="embeddable" class="gl-mb-5" :url="snippet.webUrl" />
       <div v-for="blob in blobs" :key="blob.path">
         <snippet-blob :snippet="snippet" :blob="blob" />
       </div>

app/assets/javascripts/snippets/components/snippet_blob_view.vue

@@ -97,7 +97,7 @@ export default {
       <template #actions>
         <clone-dropdown-button
           v-if="canBeCloned"
-          class="mr-2"
+          class="gl-mr-3"
           :ssh-link="snippet.sshUrlToRepo"
           :http-link="snippet.httpUrlToRepo"
           data-qa-selector="clone_button"