Resolve a FIXME

Now that we are using a newer smol_str release this can be simplified :)

crates/ra_syntax/src/syntax_text.rs

@@ -38,9 +38,7 @@ pub fn to_string(&self) -> String {
     }
 
     pub fn to_smol_string(&self) -> SmolStr {
-        // FIXME: use `self.chunks().collect()` here too once
-        // https://github.com/matklad/smol_str/pull/12 is merged and published
-        self.to_string().into()
+        self.chunks().collect()
     }
 
     pub fn contains(&self, c: char) -> bool {