cleanup of deprecated test methods

PiperOrigin-RevId: 721042185
Change-Id: Ib0c1b9d9136384807a5919ad0e9d00458d155dde

Author: Googler

tensorflow_compression/python/layers/signal_conv_test.py

@@ -376,7 +376,7 @@ def run_or_fail(self, method,
         raise
     else:
       try:
-        with self.assertRaisesRegexp(NotImplementedError, "SignalConv"):
+        with self.assertRaisesRegex(NotImplementedError, "SignalConv"):
           method(**args)
       except:
         msg = []