Bump org.assertj:assertj-core from 3.25.3 to 3.26.3 in /modules/r2dbc

Bumps [org.assertj:assertj-core](https://github.com/assertj/assertj) from 3.25.3 to 3.26.3.
- [Release notes](https://github.com/assertj/assertj/releases)
- [Commits](assertj/assertj@assertj-build-3.25.3...assertj-build-3.26.3)

---
updated-dependencies:
- dependency-name: org.assertj:assertj-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

modules/r2dbc/build.gradle

@@ -11,10 +11,10 @@ dependencies {
     api project(':testcontainers')
     api 'io.r2dbc:r2dbc-spi:0.9.0.RELEASE'
 
-    testImplementation 'org.assertj:assertj-core:3.25.3'
+    testImplementation 'org.assertj:assertj-core:3.26.3'
     testImplementation 'io.r2dbc:r2dbc-postgresql:0.8.13.RELEASE'
     testImplementation project(':postgresql')
 
     testFixturesImplementation 'io.projectreactor:reactor-core:3.6.6'
-    testFixturesImplementation 'org.assertj:assertj-core:3.25.3'
+    testFixturesImplementation 'org.assertj:assertj-core:3.26.3'
 }