Use testCompileClasspath instead of testCompileOnly

[colltoaction]

This will make the project future-proof for Gradle 7: Dependencies should no longer be declared using the compile and runtime configurations

Example build script:

plugins {
    id 'java-library'
}

repositories {
    jcenter()
}

dependencies {
    testImplementation "org.testcontainers:junit-jupiter:1.14.3"
}

Current output:

The testCompileOnly configuration has been deprecated for resolution. This will fail with an error in Gradle 7.0. Please resolve the testCompileClasspath configuration instead. Consult the upgrading guide for further information: https://docs.gradle.org/6.6.1/userguide/upgrading_version_5.html#dependencies_should_no_longer_be_declared_using_the_compile_and_runtime_configurations

FAILURE: Build failed with an exception.

* What went wrong:
Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0

[rnorth]

Thanks @colltoaction - LGTM