spanner-jdbc: Add beta note to README and cleanup pom.xml

[kolea2]

No description provided.

[kolea2]

@chingor13 please take another quick look. Thanks!

[codecov]

Codecov Report

Merging #6047 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@ Coverage Diff @@## master #6047 +/- ##
============================================
+ Coverage 47.37% 47.38% +0.01% - Complexity 27111 27118 +7 
============================================
Files 2516 2516 Lines 273718 273815 +97 Branches 31353 31354 +1 ============================================
+ Hits 129670 129754 +84 - Misses 134440 134452 +12 - Partials 9608 9609 +1

Impacted Files	Coverage Δ	Complexity Δ
.../google/cloud/vision/v1/ProductSearchSettings.java	10.14% <0%> (-0.63%)	2% <0%> (ø)
...google/cloud/vision/v1/stub/ProductSearchStub.java	3.7% <0%> (-0.3%)	1% <0%> (ø)
...le/cloud/vision/v1/stub/GrpcProductSearchStub.java	96.86% <0%> (-0.06%)	27% <0%> (+1%)
...om/google/cloud/vision/v1/ProductSearchClient.java	61.34% <0%> (-0.05%)	80% <0%> (+4%)
...loud/vision/v1/stub/ProductSearchStubSettings.java	83.15% <0%> (+1.22%)	31% <0%> (+2%)	⬆️
...e/cloud/vision/v1/stub/GrpcImageAnnotatorStub.java	90.51% <0%> (+1.97%)	12% <0%> (ø)	⬇️
...gle/cloud/storage/testing/RemoteStorageHelper.java	65.04% <0%> (ø)	9% <0%> (ø)	⬇️
.../cloud/datastore/testing/LocalDatastoreHelper.java	85.07% <0%> (ø)	17% <0%> (ø)	⬇️
.../java/com/google/cloud/testing/CommandWrapper.java	96.96% <0%> (ø)	13% <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 f7d3438...6fd2e69. Read the comment docs.