Auto merge of #18169 - upsuper:write-css-fix, r=nox

Add whitespace before line number in grid line

This is a followup fix of #18159 where the space was incorrectly removed.

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components/style/values/generics/grid.rs

@@ -58,6 +58,7 @@ impl ToCss for GridLine {
         }
 
         if let Some(i) = self.line_num {
+            dest.write_str(" ")?;
             i.value().to_css(dest)?;
         }