fix: do not modify options object, use defaultScopes

[alexander-fenster]

Regenerated the library using
gapic-generator-typescript
v1.2.1.

[codecov]

Codecov Report

Merging #497 (976e414) into master (69f9bcf) will decrease coverage by 0.02%.
The diff coverage is 97.55%.

@@            Coverage Diff             @@
##           master     #497      +/-   ##
==========================================
- Coverage   98.57%   98.55%   -0.03%     
==========================================
  Files          10       10              
  Lines       16132    16292     +160     
  Branches      371      353      -18     
==========================================
+ Hits        15902    16056     +154     
- Misses        224      230       +6     
  Partials        6        6              

Impacted Files	Coverage Δ
src/v3/alert_policy_service_client.ts	98.66% <96.47%> (-0.04%)	⬇️
src/v3/group_service_client.ts	98.62% <97.36%> (-0.03%)	⬇️
src/v3/uptime_check_service_client.ts	98.59% <97.36%> (-0.03%)	⬇️
src/v3/notification_channel_service_client.ts	98.72% <97.76%> (-0.02%)	⬇️
src/v3/service_monitoring_service_client.ts	98.67% <97.76%> (-0.02%)	⬇️
src/v3/metric_service_client.ts	98.76% <97.97%> (-0.03%)	⬇️
src/index.ts	100.00% <100.00%> (ø)

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