chore: update gapic-generator-java to 0.0.18

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PiperOrigin-RevId: 350949863
Source-Link: googleapis/googleapis@91e206b

[codecov]

Codecov Report

Merging #300 (df36e0b) into master (0cf0a7f) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #300   +/-   ##
=========================================
  Coverage     76.38%   76.38%           
  Complexity      133      133           
=========================================
  Files            12       12           
  Lines           940      940           
  Branches         12       12           
=========================================
  Hits            718      718           
  Misses          208      208           
  Partials         14       14           

Impacted Files	Coverage Δ	Complexity Δ
...om/google/cloud/billing/v1/CloudBillingClient.java	82.63% <ø> (ø)	52.00 <0.00> (ø)
...om/google/cloud/billing/v1/CloudCatalogClient.java	69.56% <ø> (ø)	11.00 <0.00> (ø)
...google/cloud/billing/v1/stub/CloudBillingStub.java	7.69% <ø> (ø)	1.00 <0.00> (ø)
...loud/billing/v1/stub/CloudBillingStubSettings.java	81.95% <ø> (ø)	20.00 <0.00> (ø)
...google/cloud/billing/v1/stub/CloudCatalogStub.java	20.00% <ø> (ø)	1.00 <0.00> (ø)
...loud/billing/v1/stub/CloudCatalogStubSettings.java	76.10% <ø> (ø)	12.00 <0.00> (ø)
...lling/v1/stub/GrpcCloudBillingCallableFactory.java	37.50% <ø> (ø)	3.00 <0.00> (ø)
...lling/v1/stub/GrpcCloudCatalogCallableFactory.java	37.50% <ø> (ø)	3.00 <0.00> (ø)

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