CSMShader: Add missing getPointShadow() argument.

[brentyi]

#28588 adds an intensity argument to the getPointShadow() function, but this wasn't updated in the CSM add-on.

If we add a point light into the CSM example:

diff --git a/examples/webgl_shadowmap_csm.html b/examples/webgl_shadowmap_csm.html
index 41bb816..7d00a08 100644
--- a/examples/webgl_shadowmap_csm.html
+++ b/examples/webgl_shadowmap_csm.html
@@ -95,6 +95,11 @@
                                const ambientLight = new THREE.AmbientLight( 0xffffff, 1.5 );
                                scene.add( ambientLight );

+                               const pointLight = new THREE.PointLight( 0xffffff, 5, 500, 0 );
+                               pointLight.castShadow = true;
+                               pointLight.position.set(-200, 150, 100);
+                               scene.add( pointLight );
+
                                const additionalDirectionalLight = new THREE.DirectionalLight( 0x000020, 1.5 );
                                additionalDirectionalLight.position.set( params.lightX, params.lightY, params.lightZ ).normalize().multiplyScalar( - 200 );
                                scene.add( additionalDirectionalLight );

Previously, we'd get a blank viewport:

And this error:

ERROR: 0:968: 'getPointShadow' : no matching overloaded function found

After this change, we can render all lights/shadows: