Bug fix: replace space indention by tab

I installed utilsnips w/ vim-snippets today and it failed from the very beginning with Perl files:

An error occured. This is either a bug in UltiSnips or a bug in a
snippet definition. If you think this is a bug, please report it to
https://github.com/SirVer/ultisnips/issues/new.

Following is the full stack trace:
Traceback (most recent call last):
  File "/home/graf/.vim/bundle/ultisnips/pythonx/UltiSnips/snippet_manager.py", line 54, in wrapper
    return func(self, *args, **kwds)
  File "/home/graf/.vim/bundle/ultisnips/pythonx/UltiSnips/snippet_manager.py", line 118, in expand
    if not self._try_expand():
  File "/home/graf/.vim/bundle/ultisnips/pythonx/UltiSnips/snippet_manager.py", line 546, in _try_expand
    snippets = self._snips(before, False)
  File "/home/graf/.vim/bundle/ultisnips/pythonx/UltiSnips/snippet_manager.py", line 461, in _snips
    source.ensure(filetypes)
  File "/home/graf/.vim/bundle/ultisnips/pythonx/UltiSnips/snippet/source/file/_base.py", line 37, in ensure
    self._load_snippets_for(ft)
  File "/home/graf/.vim/bundle/ultisnips/pythonx/UltiSnips/snippet/source/file/_base.py", line 67, in _load_snippets_for
    self._parse_snippets(ft, fn)
  File "/home/graf/.vim/bundle/ultisnips/pythonx/UltiSnips/snippet/source/file/_base.py", line 83, in _parse_snippets
    raise SnippetSyntaxError(filename, line_index, msg)
UltiSnips.snippet.source.file._base.SnippetSyntaxError: Invalid line '    use Data::Dump qw(dump);' in .dotfiles/vim/bundle/vim-snippets/snippets/perl.snippets:353