Improve ApplyQFT API docs (#1810)

library/qs_source/src/std/canon.qs

@@ -489,17 +489,22 @@ namespace Microsoft.Quantum.Canon {
     }
 
     /// # Summary
-    /// Applies Quantum Fourier Transform (QFT) to a little-endian quantum register.
+    /// Applies the rotations of Quantum Fourier Transform (QFT) to a little-endian quantum register.
     ///
     /// # Description
-    /// Applies QFT to a little-endian register `qs` of length n
-    /// containing |x₁⟩⊗|x₂⟩⊗…⊗|xₙ⟩. The qs[0] contains the
+    /// Applies the rotations of QFT to a little-endian register `qs` of length n
+    /// containing |x₁⟩⊗|x₂⟩⊗…⊗|xₙ⟩. The qs[0] initially contains the
     /// least significant bit xₙ. The state of qs[0] becomes
     /// (|0⟩+𝑒^(2π𝑖[0.xₙ])|1⟩)/sqrt(2) after the operation.
     ///
     /// # Input
     /// ## qs
-    /// Quantum register in a little-endian format to which the QFT is applied.
+    /// Quantum register in a little-endian format to which the rotations are applied.
+    ///
+    /// # Remarks
+    /// Note that this operation applies only the rotations part of the QFT.
+    /// To complete the transform, you need to reverse the order of qubits after this operation,
+    /// for example, using the operation `SwapReverseRegister`.
     ///
     /// # Reference
     ///  - [Quantum Fourier transform](https://en.wikipedia.org/wiki/Quantum_Fourier_transform)