Clear BPF data in KernelCpuUidTimeReader.removeUid()

Currently KernelCpuUidTimeReader removes BPF cputime data in
removeUidsInRange(), but not in removeUid(), causing a leak where data
for some UIDs persists after it should have been removed. Update
removeUid() so that BPF data for removed UIDs is removed in both
paths.

Bug: 174739872
Test: open Chrome app & tabs & then close them; confirm isolated UID
data is removed.
Change-Id: I46315e37c2ac21a3964bb18f8fc9e050a83f97fe
Signed-off-by: Connor O'Brien <connoro@google.com>