chore: release 2.0.0b1 (#823)

diff --git a/google/auth/version.py b/google/auth/version.py
index bd3c61a..db6d3e9 100644
--- a/google/auth/version.py
+++ b/google/auth/version.py
@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__version__ = "1.34.0"
+__version__ = "2.0.0b1"