Fix mistake in Izhikevich equation markdown

Author: rgerkin

neuronunit/examples/reduced-model-simulation.ipynb

@@ -22,7 +22,7 @@
     "\\frac{dV}{dt} & = & 0.04V^2 +5V +140 - U + I  \\\\\n",
     "\\frac{dU}{dt} & = & a(bV - U) \\\\\n",
     "\\end{matrix}\n",
-    "<center>if $v>30$, set $v=c$ and $u=u+1$"
+    "<center>if $v>30$, set $v=c$ and $u=u+d$"
    ]
   },
   {
@@ -405,7 +405,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.6"
+   "version": "3.8.3"
   }
  },
  "nbformat": 4,