Revert the change of the limit for interpolation of R0 with respect t…

…o metallic and SSR

Commit 2c000cb changed the interpolation limits from (0.04, 1.0) to (0.04, 0.37). This is incorrect, as we want to have an F0 of 0.04 for dielectrics (materials with metalness of 0.0) and an F0 of 1.0 for metals.
The Schlick approximation uses an F0 of 0.04 for all dielectrics and it's good enough.
Having it lower than 1.0 leads to an incorrect application of the Fresnel effect for metals and leads to bugs like godotengine#79549

servers/rendering/renderer_rd/shaders/effects/screen_space_reflection.glsl

@@ -263,7 +263,9 @@ void main() {
 
 		// Schlick term.
 		float metallic = texelFetch(source_metallic, ssC << 1, 0).w;
-		float f0 = mix(0.04, 0.37, metallic); // The default value of R0 is 0.04 and the maximum value is considered to be Germanium with R0 value of 0.37
+		// F0 is the reflectance of normally incident light (perpendicular to the surface).
+		// Dielectric materials have a widely accepted default value of 0.04. We assume that metals reflect all light, so their F0 is 1.0.
+		float f0 = mix(0.04, 1.0, metallic);
 		float m = clamp(1.0 - dot(normal, -view_dir), 0.0, 1.0);
 		float m2 = m * m;
 		m = m2 * m2 * m; // pow(m,5)