[Dashboard Navigation] Unskip tests (elastic#211660)

Closes elastic#210618

## Summary

This PR unskips all Links tests that were skipped since these tests are
not actually flaky at this point in time. I ran them through the FTR 200
times ([run
1](https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/7900),
[run
2](https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/7902))
to confirm this.

### Checklist

- [x] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

test/functional/apps/dashboard_elements/links/links_navigation.ts

@@ -214,9 +214,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
         expect(isDisabled).to.be('true');
       });
 
-      // TODO We should not be using an external website for our tests. This will be flaky
-      // if external network connectivity issues exist.
-      it.skip('should create an external link when openInNewTab is enabled', async () => {
+      it('should create an external link when openInNewTab is enabled', async () => {
         await testSubjects.clickWhenNotDisabled('externalLink--link999');
 
         // Should have opened another tab
@@ -227,7 +225,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
         expect(currentUrl).to.be('https://example.com/1');
       });
 
-      it.skip('should open in same tab when openInNewTab is disabled', async () => {
+      it('should open in same tab when openInNewTab is disabled', async () => {
         await testSubjects.clickWhenNotDisabled('externalLink--link888');
 
         // Should have opened in the same tab