Add missing backslash, otherwise the URL would be treated as a single command

Linux-instructions.md

@@ -6,7 +6,7 @@ With most desktop-oriented distributions, double-clicking the font file should b
 3.  ```shell
     # In download.sh
     for type in Bold Light Medium Regular Retina; do
-        wget -O ~/.local/share/fonts/FiraCode-${type}.ttf
+        wget -O ~/.local/share/fonts/FiraCode-${type}.ttf \
         "https://github.com/tonsky/FiraCode/blob/master/distr/ttf/FiraCode-${type}.ttf?raw=true";
     done
     ```