Bump software.amazon.awssdk:cloudwatch from 2.21.7 to 2.21.20 (#4340)

Bumps software.amazon.awssdk:cloudwatch from 2.21.7 to 2.21.20.

---
updated-dependencies:
- dependency-name: software.amazon.awssdk:cloudwatch
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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gradle/libs.versions.toml

@@ -9,7 +9,7 @@ awaitility = "4.2.0"
 # legacy SDK
 aws-cloudwatch = "1.12.586"
 caffeine = "2.9.3"
-cloudwatch2 = "2.21.7"
+cloudwatch2 = "2.21.20"
 colt = "1.2.0"
 dagger = "2.48.1"
 dropwizard-metrics = "4.2.22"