completion: remove broken dead code from __git_heads() and __git_tags()

completion: remove broken dead code from __git_heads() and __git_tags()

__git_heads() was introduced in 5de40f5 (Teach bash about
git-repo-config., 2006-11-27), and __git_tags() in 88e21dc (Teach bash
about completing arguments for git-tag, 2007-08-31).  As their name
suggests, __git_heads() is supposed to list only branches, and
__git_tags() only tags.

Since their introduction both of these functions consist of two
distinct parts.  The first part gets branches or tags, respectively,
from a local repositoty using 'git for-each-ref'.  The second part
queries a remote repository given as argument using 'git ls-remote'.

These remote-querying parts are broken in both functions since their
introduction, because they list both branches and tags from the remote
repository.  (The 'git ls-remote' query is not limited to list only
heads or tags, respectively, and the for loop filtering the query
results prints everything except dereferenced tags.)  This breakage
could be easily fixed by passing the '--heads' or '--tags' options or
appropriate refs patterns to the 'git ls-remote' invocations.

However, that no one noticed this breakage yet is probably not a
coincidence: neither of these two functions were used to query a
remote repository, the remote-querying parts were dead code already
upon thier introduction and remained dead ever since.

Since those parts of code are broken, are and were never used, stop
the bit-rotting and remove them.

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>