fix(deps): update zeebe-process-test.version to v8.7.15

Author: renovate[bot]

pom.xml

@@ -38,7 +38,7 @@
         For backwards compatibility we pin the version to compile to Camunda 7.20.
         -->
         <camunda.compile.version>7.20.0</camunda.compile.version>
-        <zeebe-process-test.version>8.4.5</zeebe-process-test.version>
+        <zeebe-process-test.version>8.7.15</zeebe-process-test.version>
         <spring-zeebe.version>8.3.6</spring-zeebe.version>
         <spring-boot.version>3.1.12</spring-boot.version>