Bump junit from 4.13 to 4.13.1 in /backend

Bumps [junit](https://github.com/junit-team/junit4) from 4.13 to 4.13.1.
- [Release notes](https://github.com/junit-team/junit4/releases)
- [Changelog](https://github.com/junit-team/junit4/blob/main/doc/ReleaseNotes4.13.1.md)
- [Commits](junit-team/junit4@r4.13...r4.13.1)

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

Author: dependabot[bot]

backend/pom.xml

@@ -61,7 +61,7 @@
         <json-path.version>2.4.0</json-path.version>
         <hsqldb.version>2.5.0</hsqldb.version>
         <jackson-datatype.version>2.10.3</jackson-datatype.version>
-        <junit.version>4.13</junit.version>
+        <junit.version>4.13.1</junit.version>
         <mockito.version>2.23.0</mockito.version>
         <json-schema-validator.version>2.2.10</json-schema-validator.version>
         <mysql-connector.version>8.0.19</mysql-connector.version>