nimble/Makefile: remove unnecessary warning suppression.

The -Wno-sometimes-uninitialized suppression seems to no longer be
necessary. Removing it as it may mask a real bug.

If the problem reappears, and if the comment is correct about it
being only in an unused function, then instead of adding the CFLAG,
it should be fixed locally via a patch.

pkg/nimble/Makefile

@@ -14,7 +14,6 @@ ifeq (llvm,$(TOOLCHAIN))
 # `nimble/controller/src/ble_ll_adv.c` isn't used in our compilation path, so
 # tell LLVM/clang not to be so pedantic with this.
   CFLAGS += -Wno-unused-function
-  CFLAGS += -Wno-sometimes-uninitialized
 else
   CFLAGS += -Wno-unused-but-set-variable
 endif