docs: Refresh generated code in GPU tutorial

Author: FabioLuporini

examples/performance/01_gpu.ipynb

@@ -309,7 +309,7 @@
       "    {\n",
       "      for (int y = y_m; y <= y_M; y += 1)\n",
       "      {\n",
-      "        uL0(time + 1, x + 2, y + 2) = dt*(c*(r1*uL0(time, x + 1, y + 2) + r1*uL0(time, x + 3, y + 2) + r2*uL0(time, x + 2, y + 1) + r2*uL0(time, x + 2, y + 3) - 2.0F*(r1*uL0(time, x + 2, y + 2) + r2*uL0(time, x + 2, y + 2))) + r0*uL0(time, x + 2, y + 2));\n",
+      "        uL0(time + 1, x + 2, y + 2) = dt*(c*(r1*uL0(time, x + 1, y + 2) + r1*uL0(time, x + 3, y + 2) + r2*uL0(time, x + 2, y + 1) + r2*uL0(time, x + 2, y + 3) + (-2.0F)*(r1*uL0(time, x + 2, y + 2) + r2*uL0(time, x + 2, y + 2))) + r0*uL0(time, x + 2, y + 2));\n",
       "      }\n",
       "    }\n",
       "    STOP(section0,timers)\n",