Fix typo in notebook example (#7426)

Author: pavoljuhas

docs/google/internal_gates.ipynb

@@ -124,7 +124,7 @@
     "}\n",
     "internal_gate = cirq_google.InternalGate(\n",
     "    gate_module='GATE_MODULE',  # Module of class.\n",
-    "    gate_name='GATE_NAMPE',  # Class name.\n",
+    "    gate_name='GATE_NAME',  # Class name.\n",
     "    num_qubits=2,  # Number of qubits that the gate acts on.\n",
     "    **internal_gate_args,\n",
     ")\n",
@@ -141,14 +141,14 @@
     {
      "data": {
       "text/html": [
-       "<pre style=\"overflow: auto; white-space: pre;\">0: ───GATE_MODULE.GATE_NAMPE()───\n",
+       "<pre style=\"overflow: auto; white-space: pre;\">0: ───GATE_MODULE.GATE_NAME()───\n",
        "      │\n",
-       "1: ───#2─────────────────────────</pre>"
+       "1: ───#2────────────────────────</pre>"
       ],
       "text/plain": [
-       "0: ───GATE_MODULE.GATE_NAMPE()───\n",
+       "0: ───GATE_MODULE.GATE_NAME()───\n",
        "      │\n",
-       "1: ───#2─────────────────────────"
+       "1: ───#2────────────────────────"
       ]
      },
      "execution_count": 7,