btrfs-progs: docs: drop indices from pages

At this point it's not clear what exactly needs the indices and they
appear in the left column with list of index pages which is a bit
confusing.

Signed-off-by: David Sterba <dsterba@suse.com>

Documentation/index.rst

@@ -10,9 +10,3 @@ Welcome to BTRFS documentation!
    man-index
    wiki-index
 
-
-Indices and tables
-==================
-
-* :ref:`genindex`
-* :ref:`search`

Documentation/man-index.rst

@@ -31,8 +31,3 @@ Manual pages
    btrfstune
    fsck.btrfs
    mkfs.btrfs
-
-Indices
-=======
-
-* :ref:`genindex`

Documentation/wiki-index.rst

@@ -7,8 +7,3 @@ Wiki pages
    :maxdepth: 1
 
    Glossary
-
-Indices
-=======
-
-* :ref:`genindex`