Removed dependency on money-ri-platform in money-impl/pom.xml

Removing the (unnecessary?) dependency on money-ri-platform in money-impl/pom.xml fixed the build issue.

There remain some references to money-platform-ri, as follows:

$ grep -ri "money-platform-ri" *
money-api/convert/pom.xml:			<artifactId>money-platform-ri</artifactId>
money-api/ext/pom.xml:			<artifactId>money-platform-ri</artifactId>
money-api/format/pom.xml:			<artifactId>money-platform-ri</artifactId>

and many of these use the javax.money group instead of net.java.javamoney, so it may be a wider review is required.