fix evidence rpc test by extending wait time (#6678)

rpc/client/evidence_test.go

@@ -120,7 +120,7 @@ func TestBroadcastEvidence_DuplicateVoteEvidence(t *testing.T) {
 	// previous versions of this test used a shared fixture with
 	// other tests, and in this version we give it a little time
 	// for the node to make progress before running the test
-	time.Sleep(10 * time.Millisecond)
+	time.Sleep(100 * time.Millisecond)
 
 	chainID := config.ChainID()