Remove option to clear time zone dropdown

Per UX reviewer feedback

app/assets/javascripts/pages/projects/pipeline_schedules/shared/components/timezone_dropdown.js

@@ -17,13 +17,7 @@ export const formatUtcOffset = (offset) => {
   return `${prefix} ${Math.abs(offset / 3600)}`;
 };
 
-export const formatTimezone = (item) => {
-  if (Object.prototype.hasOwnProperty.call(item, 'offset')) {
-    return `[UTC ${formatUtcOffset(item.offset)}] ${item.name}`;
-  }
-
-  return item.name;
-};
+export const formatTimezone = (item) => `[UTC ${formatUtcOffset(item.offset)}] ${item.name}`;
 
 export const findTimezoneByIdentifier = (tzList = [], identifier = null) => {
   if (tzList && tzList.length && identifier && identifier.length) {
@@ -45,15 +39,6 @@ export default class TimezoneDropdown {
     this.$input = $inputEl;
     this.timezoneData = this.$dropdown.data('data') || [];
 
-    if (allowEmpty) {
-      this.timezoneData = [
-        {
-          name: this.$dropdownToggle.text(),
-        },
-        ...this.timezoneData,
-      ];
-    }
-
     this.onSelectTimezone = onSelectTimezone;
     this.displayFormat = displayFormat || defaults.displayFormat;
     this.allowEmpty = allowEmpty;

spec/frontend/pages/projects/pipeline_schedules/shared/components/timezone_dropdown_spec.js

@@ -81,12 +81,6 @@ describe('Timezone Dropdown', () => {
         it('will default the value of the input to an empty string', () => {
           expect($inputEl.val()).toBe('');
         });
-
-        it('will add a new dropdown item for selecting an empty value', () => {
-          expect(
-            $(`${tzListSel}:contains('${findDropdownToggleText().html()}')`, $wrapper).length,
-          ).not.toBe(0);
-        });
       });
     });
 
@@ -202,14 +196,6 @@ describe('Timezone Dropdown', () => {
         }),
       ).toEqual('[UTC 0] Accra');
     });
-
-    it('returns name when no offset is provided', () => {
-      expect(
-        formatTimezone({
-          name: 'Foo bar',
-        }),
-      ).toEqual('Foo bar');
-    });
   });
 
   describe('findTimezoneByIdentifier', () => {