Fix java-pinning-core dependency in java-pinning-java7: use 'api'
Fix java-pinning-core dependency in java-pinning-java7: use 'api'

Since Java7Pinning subclasses JavaPinning, consumers of
java-pinning-java7 need to java java-pinning-core in their compliation
classpath. Hence it is not sufficient ot use 'implementation', we need
to use 'api'.

Flowdalic/java-pinning,Flowdalic/java-pinning,Flowdalic/java-pinning