Bump com.guardsquare:proguard-core from 9.1.6 to 9.1.8

Bumps [com.guardsquare:proguard-core](https://github.com/Guardsquare/proguard-core) from 9.1.6 to 9.1.8.
- [Release notes](https://github.com/Guardsquare/proguard-core/releases)
- [Commits](Guardsquare/proguard-core@v9.1.6...v9.1.8)

---
updated-dependencies:
- dependency-name: com.guardsquare:proguard-core
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pom.xml

@@ -9,7 +9,7 @@
 		<scm.revision>NO_SCM_REVISION</scm.revision>
 
 		<version.proguard>7.6.0</version.proguard>
-		<version.proguard-core>9.1.6</version.proguard-core>
+		<version.proguard-core>9.1.8</version.proguard-core>
 	</properties>