Fix a typo

Co-authored-by: Guillaume Martres <[email protected]>

Author: dwijnand

compiler/src/dotty/tools/repl/ReplCompiler.scala

@@ -88,7 +88,7 @@ class ReplCompiler extends Compiler {
     var valIdx = state.valIndex
     val defs = new mutable.ListBuffer[Tree]
 
-    /** If the user inputs a definition that's name is of the form REPL_RES_PREFIX and a number,
+    /** If the user inputs a definition whose name is of the form REPL_RES_PREFIX and a number,
      *  such as `val res9 = 1`, we bump `valIdx` to avoid name clashes.  lampepfl/dotty#3536 */
     def maybeBumpValIdx(tree: Tree): Unit = tree match
       case tuple: Tuple   => for t <- tuple.trees do maybeBumpValIdx(t)