[librsvg] filters: use enum_default macro for Input

[Paolo Borelli <pborelli src gnome org>]

commit 5db0a5168a9b2fdc1c2afe83c58ab44db8ae7124
Author: Paolo Borelli <pborelli gnome org>
Date:   Sun Mar 21 10:19:35 2021 +0100

    filters: use enum_default macro for Input

 src/filters/mod.rs | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)
---
diff --git a/src/filters/mod.rs b/src/filters/mod.rs
index 609cf160..54ce8e8f 100644
--- a/src/filters/mod.rs
+++ b/src/filters/mod.rs
@@ -108,11 +108,7 @@ pub enum Input {
     FilterOutput(CustomIdent),
 }
 
-impl Default for Input {
-    fn default() -> Self {
-        Input::Unspecified
-    }
-}
+enum_default!(Input, Input::Unspecified);
 
 impl Parse for Input {
     fn parse<'i>(parser: &mut Parser<'i, '_>) -> Result<Self, ParseError<'i>> {