gitweb: Use block form of map/grep in a few cases more

Use block form of 'grep' i.e. 'grep {BLOCK} LIST' rather than
'grep(EXPR, LIST)' in filter_snapshot_fmts subroutine.  This makes
code more readable, as expression is rather long, and statement above
there is 'map' with very similar expression also in the block form.

Remove unnecessary and misleading parentheses around block form 'map'
arguments in quote_command subroutine.

The inner "map" in format_snapshot_links was left alone, as it is not
clear whether adding parentheses or changing it into block form would
improve readibility and clarity of this code.

Signed-off-by: Jakub Narebski <redacted>
Signed-off-by: Junio C Hamano <redacted>