Bump mysql-connector-java from 8.0.30 to 8.0.31 in /modules/mysql

Bumps mysql-connector-java from 8.0.30 to 8.0.31.

---
updated-dependencies:
- dependency-name: mysql:mysql-connector-java
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

modules/mysql/build.gradle

@@ -10,7 +10,7 @@ dependencies {
     compileOnly 'dev.miku:r2dbc-mysql:0.8.2.RELEASE'
 
     testImplementation project(':jdbc-test')
-    testImplementation 'mysql:mysql-connector-java:8.0.30'
+    testImplementation 'mysql:mysql-connector-java:8.0.31'
 
     testImplementation testFixtures(project(':r2dbc'))
     testImplementation 'dev.miku:r2dbc-mysql:0.8.2.RELEASE'