jws: Fix typo in jws_test

Test is currently failing due to a missed colon during cleanup.

Change-Id: I8cef4b679b2d981ad159441bffac67b7b23862aa
Reviewed-on: https://go-review.googlesource.com/22742
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/jws/jws_test.go b/jws/jws_test.go
index d8369f6..9b5efdd 100644
--- a/jws/jws_test.go
+++ b/jws/jws_test.go
@@ -32,7 +32,7 @@
 		t.Fatal(err)
 	}
 
-	err := Verify(token, &privateKey.PublicKey)
+	err = Verify(token, &privateKey.PublicKey)
 	if err != nil {
 		t.Fatal(err)
 	}