Bump com.squareup.okio:okio from 3.9.0 to 3.9.1 in /backend

Bumps [com.squareup.okio:okio](https://github.com/square/okio) from 3.9.0 to 3.9.1.
- [Release notes](https://github.com/square/okio/releases)
- [Changelog](https://github.com/square/okio/blob/master/CHANGELOG.md)
- [Commits](square/okio@parent-3.9.0...3.9.1)

---
updated-dependencies:
- dependency-name: com.squareup.okio:okio
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

backend/build.gradle

@@ -61,7 +61,7 @@ dependencies {
      *
      * DevSecOps verifies these packages at least once per month. LAST VERIFIED: 10 July 2024.
      */
-    implementation 'com.squareup.okio:okio:3.9.0'
+    implementation 'com.squareup.okio:okio:3.9.1'
     implementation 'org.springframework:spring-core:6.0.16'
     implementation 'org.springframework.security:spring-security-core:6.1.8'
     implementation 'org.springframework.security:spring-security-oauth2-client:6.3.1'