Bump ch.qos.logback:logback-core in /deprecated/metrics-logback

Bumps [ch.qos.logback:logback-core](https://github.com/qos-ch/logback) from 1.3.12 to 1.3.15.
- [Commits](qos-ch/logback@v_1.3.12...v_1.3.15)

---
updated-dependencies:
- dependency-name: ch.qos.logback:logback-core
  dependency-type: direct:production
...

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

Author: dependabot[bot]

deprecated/metrics-logback/pom.xml

@@ -12,7 +12,7 @@
   <artifactId>avaje-metrics-logback</artifactId>
 
   <properties>
-    <logback.version>1.3.12</logback.version>
+    <logback.version>1.3.15</logback.version>
   </properties>
 
   <dependencies>