Add f128 stability attribute to FRAC_1_SQRT_2PI

Author: sunsided

library/core/src/num/f128.rs

@@ -64,11 +64,12 @@ pub mod consts {
 
     /// 1/sqrt(π)
     #[unstable(feature = "f128", issue = "116909")]
-    // Also, #[unstable(feature = "more_float_constants", issue = "103883")]
+    
     pub const FRAC_1_SQRT_PI: f128 =
         0.564189583547756286948079451560772585844050629328998856844086_f128;
 
     /// 1/sqrt(2π)
+    #[unstable(feature = "f128", issue = "116909")]
     pub const FRAC_1_SQRT_2PI: f128 =
         0.398942280401432677939946059934381868475858631164934657665926_f128;