Remove unused function GetPidByName()

Due to the fix b/132919954, this function is no longer needed.

Bug: 133223733
Test: builds
Test: All tests pass
    * First create `/data/nativetest64`:
    	adb shell mkdir /data/nativetest64
    * Then run:
        mmm -j frameworks/native/cmds/dumpstate/ \
	&& adb push ${OUT}/data/nativetest64/dumpstate_* /data/nativetest64 \
	&& adb shell /data/nativetest64/dumpstate_test/dumpstate_test
Change-Id: Id52455d8bb82909706e0b2606aa1811c9faf1d69