dim: Squelch the filter-branch warning and wait

We actually want to use git filter-branch, so make it shut
up and do what it's told.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

dim

@@ -1762,7 +1762,7 @@ function dim_extract_tags
 
 	tags=$(printf -- "$dim_extract_tags_marker\n%s" "$tags" | escape_quotes)
 
-	git filter-branch -f --msg-filter "cat ; echo \"$tags\"" $range
+	FILTER_BRANCH_SQUELCH_WARNING=1 git filter-branch -f --msg-filter "cat ; echo \"$tags\"" $range
 }
 
 function dim_extract_queued