chore: release 0.43.0

[release-please]

🤖 I have created a release *beep* *boop*

0.43.0 (2021-03-11)

Features

• add bazel support for gapic metadata (#811) (7ced24a)
• update templates to permit enum aliases (#809) (2e7ea11)

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This PR was generated with Release Please. See documentation.

[codecov]

Codecov Report

Merging #810 (49c637c) into master (7c185e8) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #810   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           26        27    +1     
  Lines         1608      1653   +45     
  Branches       328       337    +9     
=========================================
+ Hits          1608      1653   +45     

Impacted Files	Coverage Δ
gapic/utils/case.py	100.00% <ø> (ø)
gapic/utils/reserved_names.py	100.00% <ø> (ø)
gapic/generator/generator.py	100.00% <100.00%> (ø)
gapic/schema/api.py	100.00% <100.00%> (ø)
gapic/schema/wrappers.py	100.00% <100.00%> (ø)
gapic/utils/__init__.py	100.00% <100.00%> (ø)
gapic/utils/checks.py	100.00% <100.00%> (ø)
gapic/utils/options.py	100.00% <100.00%> (ø)

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[yoshi-automation]

Release is at https://github.com/googleapis/gapic-generator-python/releases/tag/v0.43.0