gitweb: Remove excessively redundant entries from git_difftree_body

gitweb: Remove excessively redundant entries from git_difftree_body

1) All entries on the left are blobs and clicking on them
leads to blobs.  No more diff or blob depending on what
happened (modified or mode changed) to the file -- this goes
to the right, in the "link" column.

2) Remove redundant "blob" from the link column on the right.
This can now be had by clicking on the entry itself.

This reduces and simplifies the code.

Signed-off-by: Luben Tuikov <redacted>
Signed-off-by: Junio C Hamano <redacted>