Omit the long-disused FTS1 and FTS2 implements from the active source tree.

Omit the long-disused FTS1 and FTS2 implements from the active source tree.
The code will persist forever in the source repository, but there is no point
in carrying it around in the latest tarballs where it is never used.

FossilOrigin-Name: 2bb50d5aedef0fd216d94058f477a58d88aa3a68bbadc94fa67998b7c391a8ff