[mlir][bazel] Remove unsed BUILD dependencies. (#87038)

This is the second attempt of 32fcfcd,
which had to be reverted.

This should be good to go now, after a number of cleanups to not expose
headers from multiple targets:

- 6e58efa
- f1dff83
- 89ef313
- eb70b48
- 83e5a12
- fce046c

Author: chsigg