chore(master): release 1.21.0

[release-please]

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

1.21.0 (2021-03-02)

Features

• generator: update protoc to v3.15.3 (#654) (4b0c59a)
• migrate to java microgenerator (#629) (60d17dc)
• publish new fields for CMEK support (#646) (e039386)

Dependencies

• update dependency com.google.cloud:google-cloud-gcloud-maven-plugin to v0.1.2 (#652) (71a8fd7)
• update dependency com.google.cloud:google-cloud-shared-dependencies to v0.20.0 (#653) (c5049c1)

---

This PR was generated with Release Please. See documentation.

[codecov]

Codecov Report

Merging #645 (b329d68) into master (4b0c59a) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #645      +/-   ##
============================================
- Coverage     83.54%   83.52%   -0.02%     
  Complexity     1198     1198              
============================================
  Files           110      110              
  Lines          7309     7309              
  Branches        383      383              
============================================
- Hits           6106     6105       -1     
- Misses         1003     1005       +2     
+ Partials        200      199       -1     

Impacted Files	Coverage Δ	Complexity Δ
...om/google/cloud/bigtable/emulator/v2/Emulator.java	59.83% <0.00%> (-0.82%)	14.00% <0.00%> (ø%)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4b0c59a...1e11e6c. Read the comment docs.

[kolea2]

holding off on release to investigate nightly failure in hbase client

[kolea2]

fixes applied, resuming release

[yoshi-automation]

🤖 Release is at https://github.com/googleapis/java-bigtable/releases/tag/v1.21.0 🌻

[release-tool-publish-reporter]

The release build has started, the log can be viewed here. 🌻

[release-tool-publish-reporter]

🥚 You hatched a release! The release build finished successfully! 💜