[mlir][async][nfc] Fix typo in async op description (#143621)

Author: javedabsar1

mlir/include/mlir/Dialect/Async/IR/AsyncOps.td

@@ -376,7 +376,7 @@ def Async_CreateGroupOp : Async_Op<"create_group", [Pure]> {
 }
 
 def Async_AddToGroupOp : Async_Op<"add_to_group", []> {
-  let summary = "adds and async token or value to the group";
+  let summary = "adds an async token or value to the group";
   let description = [{
     The `async.add_to_group` adds an async token or value to the async group.
     Returns the rank of the added element in the group. This rank is fixed
@@ -655,7 +655,7 @@ def Async_RuntimeLoadOp : Async_Op<"runtime.load",
 }
 
 def Async_RuntimeAddToGroupOp : Async_Op<"runtime.add_to_group", []> {
-  let summary = "adds and async token or value to the group";
+  let summary = "adds an async token or value to the group";
   let description = [{
     The `async.runtime.add_to_group` adds an async token or value to the async
     group. Returns the rank of the added element in the group.