Investigate removing workaround re: broken metric_descriptor path

[meredithslota]

https://github.com/googleapis/python-monitoring/blob/11f4376f6534e395c9eefe859d635dc95a360c58/owlbot.py#L41 has a comment referencing a workaround for #701. That issue was closed as "fixed" in #1089 and we should look into whether the workaround can be removed.

[parthea]

The workaround is still needed as there is still a failing test without it. I'll file a new issue in gapic-generator-python

================================================================================================================================================ FAILURES ================================================================================================================================================
______________________________________________________________________________________________________________________________________ test_metric_descriptor_path _______________________________________________________________________________________________________________________________________

    def test_metric_descriptor_path():
        project = "squid"
        metric_descriptor = "clam"
>       expected = "projects/{project}/metricDescriptors/{metric_descriptor=**}".format(
            project=project,
            metric_descriptor=metric_descriptor,
        )
E       KeyError: 'metric_descriptor=**'

tests/unit/gapic/monitoring_v3/test_metric_service.py:4133: KeyError
___________________________________________________________________________________________________________________________________ test_parse_metric_descriptor_path ____________________________________________________________________________________________________________________________________

    def test_parse_metric_descriptor_path():
        expected = {
            "project": "whelk",
            "metric_descriptor": "octopus",
        }
>       path = MetricServiceClient.metric_descriptor_path(**expected)

tests/unit/gapic/monitoring_v3/test_metric_service.py:4146: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

project = 'whelk', metric_descriptor = 'octopus'

    @staticmethod
    def metric_descriptor_path(
        project: str,
        metric_descriptor: str,
    ) -> str:
        """Returns a fully-qualified metric_descriptor string."""
>       return "projects/{project}/metricDescriptors/{metric_descriptor=**}".format(
            project=project,
            metric_descriptor=metric_descriptor,
        )
E       KeyError: 'metric_descriptor=**'

google/cloud/monitoring_v3/services/metric_service/client.py:189: KeyError