Update dependency org.apache.maven.plugins:maven-gpg-plugin to v3.2.8 (#1442)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
|
[org.apache.maven.plugins:maven-gpg-plugin](https://maven.apache.org/plugins/)
| `3.2.7` -> `3.2.8` |
[![age](https://developer.mend.io/api/mc/badges/age/maven/org.apache.maven.plugins:maven-gpg-plugin/3.2.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/maven/org.apache.maven.plugins:maven-gpg-plugin/3.2.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/maven/org.apache.maven.plugins:maven-gpg-plugin/3.2.7/3.2.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/maven/org.apache.maven.plugins:maven-gpg-plugin/3.2.7/3.2.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

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prometheus-metrics-parent/pom.xml

@@ -98,7 +98,7 @@
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-gpg-plugin</artifactId>
-            <version>3.2.7</version>
+            <version>3.2.8</version>
             <executions>
               <execution>
                 <id>sign-artifacts</id>