Bump testContainersVersion from 1.20.5 to 1.20.6 in /Plan

Bumps `testContainersVersion` from 1.20.5 to 1.20.6.

Updates `org.testcontainers:testcontainers` from 1.20.5 to 1.20.6
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.20.5...1.20.6)

Updates `org.testcontainers:junit-jupiter` from 1.20.5 to 1.20.6
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.20.5...1.20.6)

Updates `org.testcontainers:nginx` from 1.20.5 to 1.20.6
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.20.5...1.20.6)

---
updated-dependencies:
- dependency-name: org.testcontainers:testcontainers
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.testcontainers:junit-jupiter
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.testcontainers:nginx
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Plan/build.gradle

@@ -93,7 +93,7 @@ subprojects {
         junitVersion = "5.11.4"
         mockitoVersion = "5.15.2"
         seleniumVersion = "4.29.0"
-        testContainersVersion = "1.20.5"
+        testContainersVersion = "1.20.6"
         awaitilityVersion = "4.2.2"
         swaggerVersion = "2.2.28"
         guavaVersion = "33.4.0-jre"