Fix `IntegerTest`
Do not use #deepCopy with desctructive operations, #deepCopy on numbers
is an no-op (they're immutable, except internal destructive helpers)
@REM use --debug as arg to debug failed test cases
..\..\..\stx\projects\smalltalk\stx --debug --noBanner -I --execute SelfTestRunner.st
@REM ..\..\..\stx\projects\smalltalk\stx --debug --noInfoPrint --noBanner --exitOnInternalError --exitOnMessageSendError -I --execute SelfTestRunner.st