[CaR Grant] Do not offer :U .Rat/.FatRat coercers on MidRat

To be consistent with similar coercers on other numerics

Author: zoffixznet

doc/Type/MidRat.pod6

@@ -62,25 +62,21 @@ say (sqrt2 * 10⁶⁰).^name; # OUTPUT: «Rat␤»
 
 Defined as:
 
-    multi method FatRat(MidRat:U: --> FatRat:U)
-    multi method FatRat(MidRat:D: --> FatRat:D)
+    method FatRat(MidRat:D: --> FatRat:D)
 
 Coerces the invocant to a L<FatRat> object by creating a L<FatRat> with the
-same L<numerator> and L<denominator> as the invocant. If the invocant is
-a type object, simply returns a L<FatRat> type object.
+same L<numerator> and L<denominator> as the invocant.
 
 =head2 method Rat
 
 Defined as:
 
-    multi method Rat(MidRat:U: --> Rat:U)
-    multi method Rat(MidRat:D: --> Rat:D)
+    method Rat(MidRat:D: --> Rat:D)
 
 Coerces the invocant to a L<Rat>. If the denominator fits into C<uint64>, no
 precision loss occurs and a L<Rat> object with the same L<numerator> and L<denominator> as the invocant is returned. Otherwise, an operation equivalent
 to coercing the invocant to a L<Num> and then coercing that L<Num> to a L<Rat>
-is performed. If the invocant is
-a type object, simply returns a L<Rat> type object.
+is performed.
 
 =head2 method perl