Replace META/care_map.txt when signing target files

Do not copy the "META/care_map.txt" from the source zipfile when
signing the target files with sign_target_files_apks. Because we'll
generate a new care_map after rebuilding the system/vendor images;
and we'll write the new "META/care_map.txt" to the signed-target-file.

Change-Id: I6919cfdf8314a4084b5f612a9c89469f391486a4
Test: Run sign_target_files_apks locally, and the entry is updated.
Bug: 30812253