chore(dep): unpin grpc

[alexander-fenster]

gRPC v1.20.2 is out fixing the typing problems in v1.20.1, so unpinning it back.

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[codecov]

Codecov Report

Merging #475 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #475   +/-   ##
=======================================
  Coverage   88.88%   88.88%           
=======================================
  Files           1        1           
  Lines         333      333           
=======================================
  Hits          296      296           
  Misses         37       37

---

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[codecov]

Codecov Report

Merging #475 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #475   +/-   ##
=======================================
  Coverage   88.88%   88.88%           
=======================================
  Files           1        1           
  Lines         333      333           
=======================================
  Hits          296      296           
  Misses         37       37

---

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 73e0a45...1cdfbb2. Read the comment docs.