Regenerate pubsub client

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/google-cloud-clients/google-cloud-pubsub/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:6929f343c400122d85818195b18613330a12a014bffc1e08499550d40571479d
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/pubsub/artman_pubsub.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/java.
synthtool > No replacements made in **/stub/SubscriberStubSettings.java for pattern return InstantiatingGrpcChannelProvider\.newBuilder\(\);, maybe replacement is not longer needed?
synthtool > Running java formatter on 45 files
synthtool > Running java formatter on 2 files
synthtool > Running java formatter on 87 files
synthtool > Cleaned up 0 temporary directories.
synthtool > Wrote metadata to synth.metadata.

[codecov]

Codecov Report

Merging #5982 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@ Coverage Diff @@## master #5982 +/- ##
============================================
+ Coverage 46.79% 46.79% +<.01% 
Complexity 25663 25663 ============================================
Files 2456 2456 Lines 267638 267640 +2 Branches 30559 30559 ============================================
+ Hits 125245 125246 +1 - Misses 133133 133134 +1 
Partials 9260 9260

Impacted Files	Coverage Δ	Complexity Δ
...e/cloud/pubsub/v1/stub/SubscriberStubSettings.java	85.26% <100%> (+0.05%)	28 <1> (ø)	⬇️
...le/cloud/pubsub/v1/stub/PublisherStubSettings.java	84.12% <100%> (+0.06%)	20 <1> (ø)	⬇️
...ain/java/com/google/cloud/pubsub/v1/Publisher.java	89% <0%> (-0.35%)	40% <0%> (ø)

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