Remove class wrapper from stub and add self (#797)

Co-authored-by: habere <habere@dispertire.org>

Author: habere-et-dispertire

exercises/practice/rational-numbers/.meta/template-data.yaml

@@ -144,15 +144,13 @@ example: |-
     }
 
 stub: |-
-  class RationalNumbers {
     has Int $.a;
     has Int $.b;
 
-    method add (RationalNumbers $op) { }
-    method subtract (RationalNumbers $op) { }
-    method multiply (RationalNumbers $op) { }    
-    method divide (RationalNumbers $op) { }
-    method absolute { }
-    method exponent ($power) { }
-    method base ($base) { }
-  }
+    method add (RationalNumbers $op) { self }
+    method subtract (RationalNumbers $op) { self }
+    method multiply (RationalNumbers $op) { self }    
+    method divide (RationalNumbers $op) { self }
+    method absolute { self }
+    method exponent ($power) { self }
+    method base ($base) { self }

exercises/practice/rational-numbers/lib/RationalNumbers.rakumod

@@ -1,14 +1,12 @@
 unit class RationalNumbers;
 
-class RationalNumbers {
-  has Int $.a;
-  has Int $.b;
+has Int $.a;
+has Int $.b;
 
-  method add (RationalNumbers $op) { }
-  method subtract (RationalNumbers $op) { }
-  method multiply (RationalNumbers $op) { }    
-  method divide (RationalNumbers $op) { }
-  method absolute { }
-  method exponent ($power) { }
-  method base ($base) { }
-}
+method add (RationalNumbers $op) { self }
+method subtract (RationalNumbers $op) { self }
+method multiply (RationalNumbers $op) { self }    
+method divide (RationalNumbers $op) { self }
+method absolute { self }
+method exponent ($power) { self }
+method base ($base) { self }