Reapply "Merge branch '_acet-fix-expanding-context-lines' into 'master'"

This reverts commit 1c9c755a29b5f476b9c59aa784c70fdd85ec220d.

app/assets/javascripts/diffs/components/diff_line_gutter_content.vue

@@ -189,7 +189,6 @@ export default {
       </button>
       <a
         v-if="lineNumber"
-        v-once
         :data-linenumber="lineNumber"
         :href="lineHref"
       >

app/assets/javascripts/diffs/components/inline_diff_table_row.vue

@@ -101,7 +101,6 @@ export default {
       class="diff-line-num new_line"
     />
     <td
-      v-once
       :class="line.type"
       class="line_content"
       v-html="line.richText"

app/assets/javascripts/diffs/components/parallel_diff_table_row.vue

@@ -119,7 +119,6 @@ export default {
       class="diff-line-num old_line"
     />
     <td
-      v-once
       :id="line.left.lineCode"
       :class="parallelViewLeftLineType"
       class="line_content parallel left-side"
@@ -140,7 +139,6 @@ export default {
       class="diff-line-num new_line"
     />
     <td
-      v-once
       :id="line.right.lineCode"
       :class="line.right.type"
       class="line_content parallel right-side"