RFR (trivial) 8212774: Remove dead code touching Klass::_lower_dimension

[coleen.phillimore at oracle.com]

Summary: Found dead code removal while looking at usage of Compile_lock. 
This dead code doesn't have Compile_lock but other code touching 
Klass::_{upper,lower}_dimension do.

Ran mach5 tier1.

open webrev at http://cr.openjdk.java.net/~coleenp/8212774.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8212774

Thanks,
Coleen