fix: add missing call to EqualsTester#testEquals (#2307)

There needs to be a terminal call to `testEquals()` for the equals tester to do anything, this assertion is not currently being run.

This issue was found by https://errorprone.info/bugpattern/MissingTestCall

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Fixes #2292 ☕️

If you write sample code, please follow the [samples format](
https://togithub.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).

Author: cushon

google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/common/TypeTest.java

@@ -126,7 +126,8 @@ public void structWithSchema_equals() {
             StructWithSchema.fromProto(structProto.getStructType()))
         .addEqualityGroup(
             StructWithSchema.fromProto(complexStructProto.getStructType()),
-            StructWithSchema.fromProto(complexStructProto.getStructType()));
+            StructWithSchema.fromProto(complexStructProto.getStructType()))
+        .testEquals();
   }
 
   @Test