Migrate to GlButton in environments dropdown

app/assets/javascripts/feature_flags/components/environments_dropdown.vue

 <script>
 import { debounce } from 'lodash';
-import { GlDeprecatedButton, GlSearchBoxByType } from '@gitlab/ui';
+import { GlButton, GlSearchBoxByType } from '@gitlab/ui';
 import axios from '~/lib/utils/axios_utils';
 import { __ } from '~/locale';
 import { deprecatedCreateFlash as createFlash } from '~/flash';
@@ -28,7 +28,7 @@ import { deprecatedCreateFlash as createFlash } from '~/flash';
 export default {
   name: 'EnvironmentsSearchableInput',
   components: {
-    GlDeprecatedButton,
+    GlButton,
     GlSearchBoxByType,
   },
   props: {
@@ -159,19 +159,20 @@ export default {
         <div class="dropdown-content">
           <ul v-if="results.length">
             <li v-for="(result, i) in results" :key="i">
-              <gl-deprecated-button class="btn-transparent" @click="selectEnvironment(result)">{{
+              <gl-button category="tertiary" @click="selectEnvironment(result)">{{
                 result
-              }}</gl-deprecated-button>
+              }}</gl-button>
             </li>
           </ul>
           <div v-else-if="!results.length" class="text-secondary gl-p-3">
             {{ __('No matching results') }}
           </div>
           <div v-if="shouldRenderCreateButton" class="dropdown-footer">
-            <gl-deprecated-button
-              class="js-create-button btn-blank dropdown-item"
+            <gl-button
+              category="tertiary"
+              class="js-create-button dropdown-item"
               @click="createClicked"
-              >{{ composedCreateButtonLabel }}</gl-deprecated-button
+              >{{ composedCreateButtonLabel }}</gl-button
             >
           </div>
         </div>

spec/frontend/feature_flags/components/environments_dropdown_spec.js

 import MockAdapter from 'axios-mock-adapter';
 import { shallowMount } from '@vue/test-utils';
-import { GlLoadingIcon, GlDeprecatedButton, GlSearchBoxByType } from '@gitlab/ui';
+import { GlLoadingIcon, GlButton, GlSearchBoxByType } from '@gitlab/ui';
 import { TEST_HOST } from 'spec/test_constants';
 import waitForPromises from 'helpers/wait_for_promises';
 import EnvironmentsDropdown from '~/feature_flags/components/environments_dropdown.vue';
@@ -99,7 +99,7 @@ describe('Feature flags > Environments dropdown ', () => {
 
         it('emits event when a suggestion is clicked', async () => {
           const button = wrapper
-            .findAll(GlDeprecatedButton)
+            .findAll(GlButton)
             .filter(b => b.text() === 'production')
             .at(0);
           button.vm.$emit('click');
@@ -110,7 +110,7 @@ describe('Feature flags > Environments dropdown ', () => {
 
       describe('on click clear button', () => {
         beforeEach(async () => {
-          wrapper.find(GlDeprecatedButton).vm.$emit('click');
+          wrapper.find(GlButton).vm.$emit('click');
           await wrapper.vm.$nextTick();
         });
 
@@ -137,7 +137,7 @@ describe('Feature flags > Environments dropdown ', () => {
 
     it('emits create event', async () => {
       wrapper
-        .findAll(GlDeprecatedButton)
+        .findAll(GlButton)
         .at(0)
         .vm.$emit('click');
       await wrapper.vm.$nextTick();