Fix BC_SlIP_WALL casing typo in boundary conditions

The case statement used BC_SlIP_WALL (lowercase l) instead of
BC_SLIP_WALL, which would fail to match the constant defined in
m_constants.fpp, making the slip wall boundary condition unreachable
for this specific 3D boundary direction.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

src/common/m_boundary_common.fpp

@@ -275,7 +275,7 @@ contains
                             call s_symmetry(q_prim_vf, 3, 1, k, l, pb_in, mv_in)
                         case (BC_PERIODIC)
                             call s_periodic(q_prim_vf, 3, 1, k, l, pb_in, mv_in)
-                        case (BC_SlIP_WALL)
+                        case (BC_SLIP_WALL)
                             call s_slip_wall(q_prim_vf, 3, 1, k, l)
                         case (BC_NO_SLIP_WALL)
                             call s_no_slip_wall(q_prim_vf, 3, 1, k, l)