Remove -Wsign-promo

...to avoid unhelpful "passing [enum] chooses 'int' over 'unsigned int'"
warnings from those new calls to rtl::OUString::number as introduced with
63bcb139 "Replaced O[U]String::valueOf(
static_cast<> ) with O[U]String::number()."

Change-Id: I2adb16e83865bd4cba4a1650eb54bb7f5cee31e0

solenv/gbuild/platform/solaris.mk

@@ -69,7 +69,6 @@ gb_CXXFLAGS := \
 	$(gb_CXXFLAGS_COMMON) \
 	-fPIC \
 	-Wshadow \
-	-Wsign-promo \
 	-Woverloaded-virtual \
 	-Wno-non-virtual-dtor \
 

solenv/gbuild/platform/unxgcc.mk

@@ -54,7 +54,6 @@ gb_CXXFLAGS := \
 	$(gb_CXXFLAGS_COMMON) \
 	-fPIC \
 	-Wshadow \
-	-Wsign-promo \
 	-Woverloaded-virtual \
 
 ifneq ($(COM_GCC_IS_CLANG),TRUE)