Bump powerauth.version from 1.6.0-SNAPSHOT to 1.6.0

Bumps `powerauth.version` from 1.6.0-SNAPSHOT to 1.6.0.

Updates `io.getlime.security:powerauth-rest-client-spring` from 1.6.0-SNAPSHOT to 1.6.0
- [Release notes](https://github.com/wultra/powerauth-server/releases)
- [Commits](https://github.com/wultra/powerauth-server/commits/1.6.0)

Updates `io.getlime.security:powerauth-restful-security-spring` from 1.6.0-SNAPSHOT to 1.6.0
- [Release notes](https://github.com/wultra/powerauth-restful-integration/releases)
- [Commits](https://github.com/wultra/powerauth-restful-integration/commits/1.6.0)

---
updated-dependencies:
- dependency-name: io.getlime.security:powerauth-rest-client-spring
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: io.getlime.security:powerauth-restful-security-spring
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

pom.xml

@@ -104,7 +104,7 @@
 
         <!--  Wultra dependencies  -->
         <wultra-core.version>1.8.0-SNAPSHOT</wultra-core.version>
-        <powerauth.version>1.6.0-SNAPSHOT</powerauth.version>
+        <powerauth.version>1.6.0</powerauth.version>
         <powerauth-crypto.version>1.6.0-SNAPSHOT</powerauth-crypto.version>
         <powerauth-push.version>1.6.0-SNAPSHOT</powerauth-push.version>
     </properties>