deps: update dependency com.google.guava:guava-bom to v28.2-android

[athakor]

This PR contains the following updates:

Package	Update	Change
com.google.guava:guava-bom	minor	28.1-android -> 28.2-android

The new version of Guava no longer has a dependency on org.codehaus.mojo:animal-sniffer-annotations
Fixes #3

[codecov]

Codecov Report

Merging #16 into master will increase coverage by 0.13%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master      #16      +/-   ##
============================================
+ Coverage     81.62%   81.75%   +0.13%     
  Complexity      532      532              
============================================
  Files            46       46              
  Lines          2286     2286              
  Branches        251      251              
============================================
+ Hits           1866     1869       +3     
+ Misses          300      297       -3     
  Partials        120      120

Impacted Files	Coverage Δ	Complexity Δ
.../cloud/datastore/testing/LocalDatastoreHelper.java	85.07% <0%> (+4.47%)	17% <0%> (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 7bbe181...8516085. Read the comment docs.

[BenWhitehead]

OS X Build issues are not related to the PR and have been addressed separately.