Update enum Regions.java with latest regions

[SeventhOfNine]

Add latest regions:

• asia-northeast2
• europe-west6

Fixes ##5744

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here (e.g. I signed it!) and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[SeventhOfNine]

I signed it!

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[codecov]

Codecov Report

Merging #5745 into master will decrease coverage by 0.2%.
The diff coverage is 100%.

@@ Coverage Diff @@## master #5745 +/- ##
============================================
- Coverage 46.91% 46.71% -0.21% + Complexity 25078 23629 -1449 
============================================
Files 2389 2389 Lines 259743 254611 -5132 Branches 29388 29255 -133 ============================================
- Hits 121871 118933 -2938 + Misses 128487 127626 -861 + Partials 9385 8052 -1333

Impacted Files	Coverage Δ	Complexity Δ
...rc/main/java/com/google/cloud/compute/Regions.java	93.75% <100%> (+0.41%)	4 <0> (ø)	⬇️
...igtable/gaxx/retrying/ApiResultRetryAlgorithm.java	30.76% <0%> (ø)	6% <0%> (ø)	⬇️
...gle/cloud/compute/deprecated/ForwardingRuleId.java	75% <0%> (ø)	5% <0%> (ø)	⬇️
...com/google/cloud/compute/deprecated/AddressId.java	75% <0%> (ø)	5% <0%> (ø)	⬇️
...m/google/cloud/compute/deprecated/OperationId.java	76.92% <0%> (ø)	5% <0%> (ø)	⬇️
.../bigtable/admin/v2/BigtableTableAdminSettings.java	71.73% <0%> (ø)	7% <0%> (ø)	⬇️
...mpute/deprecated/StandardNetworkConfiguration.java	78.57% <0%> (ø)	10% <0%> (ø)	⬇️
...com/google/cloud/bigquery/GoogleSheetsOptions.java	73.07% <0%> (ø)	8% <0%> (ø)	⬇️
...cloud/compute/deprecated/NetworkConfiguration.java	81.25% <0%> (ø)	7% <0%> (ø)	⬇️
...va/com/google/cloud/storage/spi/v1/StorageRpc.java	62.85% <0%> (ø)	0% <0%> (ø)	⬇️
... and 1808 more

---

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 a7870fe...c39f7a1. Read the comment docs.