Minor notebook update

docs/source/notebooks/particles-formulary-completed.ipynb

@@ -1091,7 +1091,7 @@
     "\n",
     "When the reconnection layer thickness is shorter than the **ion inertial length**, $d_i ≡ c/ω_{pi}$, collisionless effects and the Hall effect enable reconnection to be fast (Zweibel & Yamada 2009). The inner electron diffusion region has a thickness of about the **electron inertial length**, $d_e ≡ c/ω_{pi}$. (Here, $ω_{pi}$ and $ω_{pe}$ are the ion and electron plasma frequencies.)\n",
     "\n",
-    "**Our goal: calculate $d_i$ and $d_e$ to get an idea of how far the MMS spacecraft should be separated from each other to investigate reconnection.**"
+    "Our goal: calculate $d_i$ and $d_e$ to get an idea of how far the MMS spacecraft should be separated from each other to investigate reconnection."
    ]
   },
   {