Update microstrip.pro

Electrostatics/microstrip.pro

@@ -29,7 +29,7 @@
    constitutive law leads to a scalar Poisson equation in terms of the electric
    potential: -Div(epsilon Grad v) = rho.
 
-   We consider here the special case where rho = 0, to model a conducting
+   We consider here the special case where rho = 0 to model a conducting
    microstrip line on top of a dielectric substrate. A Dirichlet boundary
    condition sets the potential to 1 mV on the boundary of the microstrip line
    (called "Electrode" below) and 0 V on the ground. A homogeneous Neumann