Improve template formatting in content panes.

app/assets/javascripts/issuable/time_tracking/components/estimate_only_pane.js.es6

@@ -2,6 +2,11 @@
   Vue.component('time-tracking-estimate-only-pane', {
     name: 'time-tracking-estimate-only-pane',
     props: ['timeEstimateHuman'],
-    template: '<div class="time-tracking-estimate-only-pane"><span class="bold">Estimated:</span> {{ timeEstimateHuman }}</div>',
+    template: `
+      <div class='time-tracking-estimate-only-pane'>
+        <span class='bold'>Estimated:</span>
+        {{ timeEstimateHuman }}
+      </div>
+    `,
   });
 })(window.gl || (window.gl = {}));

app/assets/javascripts/issuable/time_tracking/components/no_tracking_pane.js.es6

 ((gl) => {
   Vue.component('time-tracking-no-tracking-pane', {
     name: 'time-tracking-no-tracking-pane',
-    template: '<div class="time-tracking-no-tracking-pane"><span class="no-value">No estimate or time spent</span></div>',
+    template: `
+      <div class='time-tracking-no-tracking-pane'>
+        <span class='no-value'>No estimate or time spent</span>
+      </div>
+    `,
   });
 })(window.gl || (window.gl = {}));

app/assets/javascripts/issuable/time_tracking/components/spent_only_pane.js.es6

@@ -2,6 +2,11 @@
   Vue.component('time-tracking-spent-only-pane', {
     name: 'time-tracking-spent-only-pane',
     props: ['timeSpentHuman'],
-    template: '<div class="time-tracking-spend-only-pane"><span class="bold">Spent:</span> {{ timeSpentHuman }}</div>',
+    template: `
+      <div class='time-tracking-spend-only-pane'>
+        <span class='bold'>Spent:</span>
+        {{ timeSpentHuman }}
+      </div>
+    `,
   });
 })(window.gl || (window.gl = {}));