Regenerate monitoring 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-monitoring/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:9aed6bbde54e26d2fcde7aa86d9f64c0278f741e58808c46573e488cbf6098f0
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/monitoring/artman_monitoring.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/java.
synthtool > Running java formatter on 48 files
synthtool > Running java formatter on 5 files
synthtool > Running java formatter on 153 files
synthtool > Cleaned up 0 temporary directories.
synthtool > Wrote metadata to synth.metadata.

[codecov]

Codecov Report

Merging #5956 into master will increase coverage by 0.01%.
The diff coverage is 79.59%.

@@ Coverage Diff @@## master #5956 +/- ##
============================================
+ Coverage 46.79% 46.81% +0.01% - Complexity 25648 25666 +18 
============================================
Files 2456 2456 Lines 267613 267760 +147 Branches 30563 30566 +3 ============================================
+ Hits 125241 125359 +118 - Misses 133113 133139 +26 - Partials 9259 9262 +3

Impacted Files	Coverage Δ	Complexity Δ
...itoring/v3/NotificationChannelServiceSettings.java	12.28% <0%> (-2.31%)	2 <0> (ø)
...toring/v3/stub/NotificationChannelServiceStub.java	7.69% <0%> (-2.31%)	1 <0> (ø)
...ng/v3/stub/GrpcNotificationChannelServiceStub.java	95.65% <100%> (+1.59%)	17 <3> (+3)	⬆️
...onitoring/v3/NotificationChannelServiceClient.java	64.49% <61.76%> (-0.69%)	43 <12> (+12)
...3/stub/NotificationChannelServiceStubSettings.java	77.67% <84.84%> (+1.3%)	20 <3> (+3)	⬆️
...ain/java/com/google/cloud/pubsub/v1/Publisher.java	89.34% <0%> (+0.34%)	40% <0%> (ø)	⬇️

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