Bump minimum OpenTelemetry version to support type checks

[plamut]

See the following comment for details: #1036 (comment)

If confirmed, we should bump to at least opentelemetry-*==1.1.0, and adjust our OpenTelemetry logic to the changes in the library API.

[tswast]

Good discovery. Bummer there were breaking changes.

Looks like Spanner has already updated, so we'll need this for compatibility with them as well. googleapis/python-spanner#358

[plamut]

I see they bumped it to >= 1.1.0, thus we should probably just do the same.

[tswast]

Switching to type bug, since I believe our client will break if installed in the same environment as a Spanner client (and opentelemetry is installed)