fs_mgr: Drop some unneeded dependencies.

libfs_mgr doesn't have direct dependencies on libfec_rs / libkeyutils /
libsquashfs_utils. They were only needed when libfec and libext4_utils
were statically linked into libfs_mgr.

Bug: 112494634
Test: `m -j installclean && m -j bootimage` with aosp_taimen-userdebug.
      Check the installed files in recovery image.
Test: `mmma -j system/core/fs_mgr`
Change-Id: I4b12c2df344fabba4942b6db943cf43a031b591d