Fix typo in signal-processing.ipynb (#769)

Fix typo in signal-processing.ipynb

Author: schrodinteq

samples/quantum-signal-processing/signal-processing.ipynb

@@ -244,7 +244,7 @@
         "def qsp_circuit(x, phases):\n",
         "    \"\"\"Creates a single-qubit unitary for some given QSP phases\"\"\"\n",
         "\n",
-        "    # Map SumPy phases into NumPy phases and reverse them (gate application\n",
+        "    # Map SymPy phases into NumPy phases and reverse them (gate application\n",
         "    # direction is opposite to matrix multiplication)\n",
         "    np_phases = [float(phi) for phi in phases]\n",
         "    np_phases.reverse()\n",
@@ -547,4 +547,4 @@
   },
   "nbformat": 4,
   "nbformat_minor": 2
-}
+}