Fix a bunch of compiler warnings

[cb372]

What this does?

Use scala-collection-compat to fix deprecation warnings.

Checklist

• Reviewed the diff to look for typos, println and format errors.
• Updated the docs accordingly.

[codecov]

Codecov Report

Merging #882 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #882   +/-   ##
=======================================
  Coverage   86.28%   86.28%           
=======================================
  Files          57       57           
  Lines         824      824           
  Branches        5        5           
=======================================
  Hits          711      711           
  Misses        113      113           

Impacted Files	Coverage Δ
.../scala/higherkindness/mu/rpc/channel/package.scala	100.00% <ø> (ø)
...kindness/mu/rpc/kafka/kafkaManagementService.scala	55.29% <ø> (ø)
...ess/mu/rpc/server/handlers/GrpcServerHandler.scala	100.00% <ø> (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 429d465...0d7e5e4. Read the comment docs.