Bump version number to 1.11.0 (#1495)
Bump version number to 1.11.0 (#1495)

Motivation:

We plan on tagging a release soon.

Modifications:

- Bump the version to 1.11.0

Result:

The version in the default user-agent string will match the released
version.
grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift