[console] Restore font size flaky test (elastic#197691)

## Summary

The test no longer appears flaky based on the flaky test runner. In
addition to this PR there's also
elastic#197563 for 400+ passes. It should
be noted that in one run 25 runs were skipped and one run failed due to
an unrelated test.

Closes elastic#193868

test/functional/apps/console/_misc_console_behavior.ts

@@ -154,8 +154,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
       await PageObjects.console.openConsole();
     });
 
-    // Failing: See https://github.com/elastic/kibana/issues/193868
-    describe.skip('customizable font size', () => {
+    describe('customizable font size', () => {
       it('should allow the font size to be customized', async () => {
         await PageObjects.console.openConfig();
         await PageObjects.console.setFontSizeSetting(20);

test/functional/page_objects/console_page.ts

@@ -9,6 +9,7 @@
 
 import { Key } from 'selenium-webdriver';
 import { asyncForEach } from '@kbn/std';
+import expect from '@kbn/expect';
 import { FtrService } from '../ftr_provider_context';
 
 export class ConsolePageObject extends FtrService {
@@ -368,10 +369,12 @@ export class ConsolePageObject extends FtrService {
   public async setFontSizeSetting(newSize: number) {
     // while the settings form opens/loads this may fail, so retry for a while
     await this.retry.try(async () => {
+      const newSizeString = String(newSize);
       const fontSizeInput = await this.testSubjects.find('setting-font-size-input');
       await fontSizeInput.clearValue({ withJS: true });
       await fontSizeInput.click();
-      await fontSizeInput.type(String(newSize));
+      await fontSizeInput.type(newSizeString);
+      expect(await fontSizeInput.getAttribute('value')).to.be(newSizeString);
     });
   }