chore(deps): update dependency com.google.cloud:libraries-bom to v18

[renovate-bot]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
com.google.cloud:libraries-bom	17.0.0 -> 18.0.0

---

Renovate configuration

📅 Schedule: At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻️ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR has been generated by WhiteSource Renovate. View repository job log here.

[codecov]

Codecov Report

Merging #914 (3b6ab5c) into master (b2b1191) will decrease coverage by 1.99%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #914      +/-   ##
============================================
- Coverage     85.23%   83.23%   -2.00%     
+ Complexity     2652     2558      -94     
============================================
  Files           145      145              
  Lines         14358    11542    -2816     
  Branches       1391     1131     -260     
============================================
- Hits          12238     9607    -2631     
+ Misses         1537     1402     -135     
+ Partials        583      533      -50     

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/com/google/cloud/spanner/Database.java	57.14% <0.00%> (-11.28%)	15.00% <0.00%> (ø%)
...va/com/google/cloud/spanner/spi/v1/SpannerRpc.java	68.75% <0.00%> (-7.73%)	0.00% <0.00%> (ø%)
...a/com/google/cloud/spanner/SpannerRetryHelper.java	70.58% <0.00%> (-6.69%)	3.00% <0.00%> (ø%)
...ain/java/com/google/cloud/spanner/SessionImpl.java	80.39% <0.00%> (-6.44%)	30.00% <0.00%> (ø%)
...spanner/admin/database/v1/DatabaseAdminClient.java	76.84% <0.00%> (-6.38%)	72.00% <0.00%> (-28.00%)
...ava/com/google/cloud/spanner/v1/SpannerClient.java	75.92% <0.00%> (-6.13%)	49.00% <0.00%> (-14.00%)
.../cloud/spanner/connection/StatementResultImpl.java	79.54% <0.00%> (-5.94%)	20.00% <0.00%> (ø%)
...spanner/admin/instance/v1/InstanceAdminClient.java	73.33% <0.00%> (-5.81%)	42.00% <0.00%> (-14.00%)
...ner/connection/ClientSideStatementSetExecutor.java	80.00% <0.00%> (-5.37%)	5.00% <0.00%> (ø%)
.../cloud/spanner/spi/v1/SpannerErrorInterceptor.java	54.83% <0.00%> (-5.17%)	3.00% <0.00%> (ø%)
... and 91 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 b2b1191...3b6ab5c. Read the comment docs.