build(deps): Bump com.squareup.okio:okio from 2.9.0 to 3.4.0 in /server

Bumps [com.squareup.okio:okio](https://github.com/square/okio) from 2.9.0 to 3.4.0.
- [Changelog](https://github.com/square/okio/blob/master/CHANGELOG.md)
- [Commits](square/okio@parent-2.9.0...parent-3.4.0)

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

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

server/appengine/build.gradle

@@ -53,7 +53,7 @@ dependencies {
     implementation 'com.googlecode.objectify:objectify:5.1.22'
 
     // Force older version of okio
-    implementation 'com.squareup.okio:okio:2.9.0'
+    implementation 'com.squareup.okio:okio:3.4.0'
 
     implementation deps.gson
     implementation deps.wire.gson