Update (typo) matrix-inversion-manual.jl (#256)

Corrected "sentivity" to  "sensitivity"

Author: mzagorowska

docs/src/examples/matrix-inversion-manual.jl

@@ -130,7 +130,7 @@ value.(x)
 
 dual.(cons)
 
-# set sentivitity
+# set sensitivitity
 
 MOI.set(
     model,