Remove (apparent) unneeded Tk_GetUid() calls #448

Job	Run time
build (gcc)	1m 38s
build (gcc, CFLAGS=-DTK_NO_DEPRECATED=1)	1m 33s
test (gcc)	4m 2s
build (gcc, --disable-xft)	2m 0s
test (gcc, --disable-xft)	4m 15s
build (gcc, --disable-xss)	1m 39s
test (gcc, --enable-symbols)	3m 27s
build (gcc, --enable-symbols)	2m 0s
build (clang)	1m 48s
build (clang, CFLAGS=-DTK_NO_DEPRECATED=1)	2m 20s
build (clang, --disable-xft)	1m 50s
build (clang, --disable-xss)	2m 19s
build (clang, --enable-symbols)	1m 25s
	30m 16s

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