Tweak SSRL performance cost in 3D antialiasing comparison table

The screen-space roughness limiter's performance cost is very low
compared to other antialiasing methods (typically in the same
ballpark as FXAA).

tutorials/3d/3d_antialiasing.rst

@@ -306,7 +306,7 @@ Antialiasing comparison
 +--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+
 | Ghosting artifacts       | 🟢 None                  | 🔴 Yes                   | 🔴 Yes                   | 🟢 None                  | 🟢 None                  | 🟢 None                  |
 +--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+
-| Performance cost         | 🟡 Medium                | 🟡 Medium                | 🔴 High                  | 🟢 Low                   | 🔴 Very High             | 🟡 Medium                |
+| Performance cost         | 🟡 Medium                | 🟡 Medium                | 🔴 High                  | 🟢 Low                   | 🔴 Very High             | 🟢 Low                   |
 +--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+
 | Forward+                 | ✔️ Yes                   | ✔️ Yes                   | ✔️ Yes                   | ✔️ Yes                   | ✔️ Yes                   | ✔️ Yes                   |
 +--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+