Pass 'radius' to blur APIs instead of 'sigma'

Requires mutter!1908 first.

So now consumers of the clutter blur code don't have to know the
implementation is Gaussian and no longer need to convert the intended
blur radius to a sigma value.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1905>

js/ui/unlockDialog.js

@@ -30,7 +30,7 @@ const FADE_OUT_TRANSLATION = 200;
 const FADE_OUT_SCALE = 0.3;
 
 const BLUR_BRIGHTNESS = 0.65;
-const BLUR_SIGMA = 45;
+const BLUR_RADIUS = 90;
 
 const SUMMARY_ICON_SIZE = 32;
 
@@ -668,7 +668,7 @@ export const UnlockDialog = GObject.registerClass({
             if (effect) {
                 effect.set({
                     brightness: BLUR_BRIGHTNESS,
-                    sigma: BLUR_SIGMA * themeContext.scale_factor,
+                    radius: BLUR_RADIUS * themeContext.scale_factor,
                 });
             }
         }