Update python/doc/usecases/use_case_stiffened_panel.rst

Co-authored-by: Michael Baudin <31351465+mbaudin47@users.noreply.github.com>

python/doc/usecases/use_case_stiffened_panel.rst

@@ -101,7 +101,7 @@ and its stiffener. They are given by:
 .. math::
    q_1=\tau_{xy}t_s=2G_sh_0t_s\frac{\partial^2w}{\partial x\partial y}
 
-and
+and:
 
 .. math::
   q_c=\frac{G_ct_cp}{\ell}\left[h-2h_0+\frac{h_c}{2p}(f_1-f_2)\right]\frac{\partial^2w}{\partial x\partial y}