Convert expect to assert style in tests

We primarily use the "TDD" style assert syntax, but had a few cases of
the "BDD" style expect syntax in our code (mainly for dom asserts). They
are equivalent so we should stick to one. This also reduces our globals
(see common-test-setup.ts), which can be further reduced in following
changes.

https://www.chaijs.com/guide/styles/

Release-Notes: skip
Change-Id: I5e18dfd2804a04e66b7699e5967a33fc4cc41398
diff --git a/polygerrit-ui/app/elements/core/gr-smart-search/gr-smart-search_test.ts b/polygerrit-ui/app/elements/core/gr-smart-search/gr-smart-search_test.ts
index f269200..aa0071e 100644
--- a/polygerrit-ui/app/elements/core/gr-smart-search/gr-smart-search_test.ts
+++ b/polygerrit-ui/app/elements/core/gr-smart-search/gr-smart-search_test.ts
@@ -20,9 +20,10 @@
   });
 
   test('renders', () => {
-    expect(element).shadowDom.to.equal(/* HTML */ `
-      <gr-search-bar id="search"> </gr-search-bar>
-    `);
+    assert.shadowDom.equal(
+      element,
+      /* HTML */ ' <gr-search-bar id="search"> </gr-search-bar> '
+    );
   });
 
   test('Autocompletes accounts', () => {