Remove some debug error printing code added in JDK-8017163

JDK-8017163 added some debug code when printing remembered set failures:

[171.616s][1632757560415ms][error][gc,verify ] GC(129) Missing rem set entry:
[171.616s][1632757560415ms][error][gc,verify ] GC(129) Field 0x00000007fb1008f0 of obj 0x00000007fb1008d8 in region 1485:(O)[0x00000007fb000000,0x00000
[171.616s][1632757560415ms][error][gc,verify ] GC(129) NULL card setjava.lang.invoke.MethodType$ConcurrentWeakInternSet$WeakEntry
[...]
points to obj 0x00000004d9abd4c8 in region 683:(S)[0x00000004d9000000,0x00000004da000000,0x00000004da000000] remset Complete



I.e. the above "NULL card set" string which would indicate which card set container does not have the requested remembered set entry. This is unnecessary information, as the "points to obj" string later shows that there should be a remset to this region already.

Noticed once more during investigation of JDK-8274340.