deps: Update github.com/tdewolff/minify/v2 v2.20.9 => v2.20.13

KeepConditionalComments was deprecated in the upstream library and replaced with KeepSpecialComments. This new option reflects that both conditional comments and Server Side Include comments can be optionally stripped by the minifier. As with KeepConditionalComments, the minifier is configured not to strip them by default.

data/docs.yaml

@@ -1265,7 +1265,7 @@ config:
         precision: 0
       html:
         keepComments: false
-        keepConditionalComments: true
+        keepSpecialComments: true
         keepDefaultAttrVals: true
         keepDocumentTags: true
         keepEndTags: true