Bump HikariCP from 4.0.2 to 4.0.3 in /backend

Bumps [HikariCP](https://github.com/brettwooldridge/HikariCP) from 4.0.2 to 4.0.3.
- [Release notes](https://github.com/brettwooldridge/HikariCP/releases)
- [Changelog](https://github.com/brettwooldridge/HikariCP/blob/dev/CHANGES)
- [Commits](brettwooldridge/HikariCP@HikariCP-4.0.2...HikariCP-4.0.3)

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

backend/build.gradle

@@ -81,7 +81,7 @@ subprojects {
         implementation("org.jetbrains.exposed:exposed-dao:${exposedVersion}")
         implementation("org.jetbrains.exposed:exposed-jdbc:${exposedVersion}")
 
-        implementation 'com.zaxxer:HikariCP:4.0.2'
+        implementation 'com.zaxxer:HikariCP:4.0.3'
 
         //JDBC Drivers
         implementation 'org.xerial:sqlite-jdbc:3.34.0'