build(deps): bump logback-core.version in /apps/backend

Bumps `logback-core.version` from 1.5.18 to 1.5.20.

Updates `ch.qos.logback:logback-core` from 1.5.18 to 1.5.20
- [Release notes](https://github.com/qos-ch/logback/releases)
- [Commits](qos-ch/logback@v_1.5.18...v_1.5.20)

Updates `ch.qos.logback:logback-classic` from 1.5.18 to 1.5.20
- [Release notes](https://github.com/qos-ch/logback/releases)
- [Commits](qos-ch/logback@v_1.5.18...v_1.5.20)

---
updated-dependencies:
- dependency-name: ch.qos.logback:logback-core
  dependency-version: 1.5.20
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: ch.qos.logback:logback-classic
  dependency-version: 1.5.20
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

apps/backend/pom.xml

@@ -45,7 +45,7 @@
         <!-- Spring transitive versions -->
         <postgresql.version>42.7.7</postgresql.version>
 
-        <logback-core.version>1.5.18</logback-core.version>  <!-- https://github.com/navikt/team-catalog/security/dependabot/196 -->
+        <logback-core.version>1.5.20</logback-core.version>  <!-- https://github.com/navikt/team-catalog/security/dependabot/196 -->
     </properties>
 
     <dependencyManagement>