Fix min JDK version regression

[lbalmaceda]

Changes

PR #501 removed by mistake a line that was making the library compatible with JDK 8. Since we don't intend to introduce breaking changes during minor releases, this PR re-adds that line.

References

https://app.circleci.com/pipelines/github/auth0/auth0-java-mvc-common/212/workflows/b61e1971-39b7-4237-bda5-64acaec6c67d/jobs/305

Testing

Tested from mvc-commons library.

Before:

./gradlew clean build test

> Task :compileJava FAILED
/Users/lbalmaceda/Java/auth0-java-mvc-common/src/main/java/com/auth0/IdTokenVerifier.java:3: error: cannot access DecodedJWT
import com.auth0.jwt.interfaces.DecodedJWT;
                               ^
  bad class file: /Users/lbalmaceda/.gradle/caches/modules-2/files-2.1/com.auth0/java-jwt/3.18.0/72d9c4836cba9abf6c1b3471e262976e3d831b8a/java-jwt-3.18.0.jar(com/auth0/jwt/interfaces/DecodedJWT.class)
    class file has wrong version 55.0, should be 52.0
    Please remove or make sure it appears in the correct subdirectory of the classpath.

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'

After:

./gradlew clean build test

> Task :compileTestJava
Note: /Users/lbalmaceda/Java/auth0-java-mvc-common/src/test/java/com/auth0/AuthenticationControllerTest.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

BUILD SUCCESSFUL in 11s