fix header level

Author: dangunter

idaes/core/util/structfs/fsrunner.py

@@ -173,7 +173,7 @@ def annotate_var(
 
         - ValueError: if `is_input` and `is_output` are both False
 
-        ### Example
+        # Example
 
         Here is an example of annotating a single Pyomo variable.
         You can apply this same technique to any Pyomo, and thus IDAES,