Bump aws-v2.version from 2.18.15 to 2.18.21

Bumps `aws-v2.version` from 2.18.15 to 2.18.21.

Updates `aws-query-protocol` from 2.18.15 to 2.18.21

Updates `aws-xml-protocol` from 2.18.15 to 2.18.21

Updates `s3` from 2.18.15 to 2.18.21

Updates `url-connection-client` from 2.18.15 to 2.18.21

Updates `utils` from 2.18.15 to 2.18.21
- [Release notes](https://github.com/aws/aws-sdk-java-v2/releases)
- [Changelog](https://github.com/aws/aws-sdk-java-v2/blob/master/CHANGELOG.md)
- [Commits](aws/aws-sdk-java-v2@2.18.15...2.18.21)

---
updated-dependencies:
- dependency-name: software.amazon.awssdk:aws-query-protocol
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: software.amazon.awssdk:aws-xml-protocol
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: software.amazon.awssdk:s3
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: software.amazon.awssdk:url-connection-client
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: software.amazon.awssdk:utils
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -89,7 +89,7 @@
   </distributionManagement>
 
   <properties>
-    <aws-v2.version>2.18.15</aws-v2.version>
+    <aws-v2.version>2.18.21</aws-v2.version>
 
     <aws.version>1.12.340</aws.version>
     <checkstyle.version>10.4</checkstyle.version>