HighlightingAssets: Inline absolute_path

Its name is confusing, because it does not always hold an absolute path. Get rid
of this problem by inlining it.

src/assets.rs

@@ -212,10 +212,9 @@ impl HighlightingAssets {
 
         let path_syntax = if let Some(path) = path {
             // If a path was provided, we try and detect the syntax based on extension mappings.
-            let absolute_path =
-                PathAbs::new(path).map_or_else(|_| path.to_owned(), |p| p.as_path().to_path_buf());
-
-            match mapping.get_syntax_for(absolute_path) {
+            match mapping.get_syntax_for(
+                PathAbs::new(path).map_or_else(|_| path.to_owned(), |p| p.as_path().to_path_buf()),
+            ) {
                 Some(MappingTarget::MapToUnknown) => {
                     Err(Error::UndetectedSyntax(path.to_string_lossy().into()))
                 }