Prepare for fix to flutter/flutter#109339. (Baseflow#102)

Currently, in some circumstances where a subclasses of
`PlatformInterface` erroneously uses `implements` rather than
`extends`, a `NoSuchMethodError` will be thrown (in spite of the
documentation at
https://pub.dev/documentation/plugin_platform_interface/latest/plugin_platform_interface/PlatformInterface/verify.html
claiming that `AssertionError` will be thrown).

After flutter/flutter#109339 is fixed, the
correct type of exception will be thrown.  To avoid a test breakage in
`geocoding_platform_interface_test.dart` when the fix happens, we need
to modify the test so that it doesn't care what kind of exception is
thrown.

Author: stereotype441

Diff for: geocoding_platform_interface/test/geocoding_platform_interface_test.dart

@@ -19,7 +19,14 @@ void main() {
     test('Cannot be implemented with `implements`', () {
       expect(() {
         GeocodingPlatform.instance = ImplementsGeocodingPlatform();
-      }, throwsNoSuchMethodError);
+        // In versions of `package:plugin_platform_interface` prior to fixing
+        // https://github.com/flutter/flutter/issues/109339, an attempt to
+        // implement a platform interface using `implements` would sometimes
+        // throw a `NoSuchMethodError` and other times throw an
+        // `AssertionError`.  After the issue is fixed, an `AssertionError` will
+        // always be thrown.  For the purpose of this test, we don't really care
+        // what exception is thrown, so just allow any exception.
+      }, throwsA(anything));
     });
 
     test('Can be extended', () {