change resolution in cam exercise to make it faster

Author: cecilehannay

notebooks/challenge/cam/exercise_3.ipynb

@@ -25,7 +25,7 @@
     "<div class=\"alert alert-info\">\n",
     "<strong>Exercise: Customize your CAM history files</strong><br><br>\n",
     " \n",
-    "Create, configure, build and run a case called `fhist.1850` with the compset FHIST at the resolution `f09_f09_mg17` using the same history file output as in the control. \n",
+    "Create, configure, build and run a case called `fhist.1850` with the compset FHIST at the resolution `f19_f19_mg17` using the same history file output as in the control. \n",
     "- Use initialization datasets from a previous case. <br> For instance, use the data from the run: `b.e21.B1850.f19_g17.CMIP6-piControl-2deg.001` at year `321`\n",
     "- Start model in `1850`. \n",
     "- Run for 5 days. \n",