Trac #27173: p_group_cohomology missing dependencies

The API change of `coercion_model` (#27021) broke `p_group_cohomology`.

- patchbot report: https://patchbot.sagemath.org/log/27152/Ubuntu/18.04/
x86_64/4.15.0-38-generic/quasar/2019-01-29%2023:36:43

Rebuilding `p_group_cohomology` is sufficient (an analogous problem
occurred with `giacpy_sage` on #27021).

As experimental fix, we make `p_group_cohomology` depend on
`element.pxd` and cython.

URL: https://trac.sagemath.org/27173
Reported by: jdemeyer
Ticket author(s): Jeroen Demeyer, Simon King
Reviewer(s): Simon King, Jeroen Demeyer

build/pkgs/p_group_cohomology/dependencies

@@ -1 +1 @@
-singular meataxe | matplotlib gap xz $(SAGERUNTIME)
+$(PYTHON) cython cysignals singular meataxe $(SAGE_SRC)/sage/matrix/matrix_gfpn_dense.pxd $(SAGE_SRC)/sage/structure/element.pxd $(SAGE_SRC)/sage/matrix/matrix_gfpn_dense.pxd $(SAGE_SRC)/sage/matrix/matrix0.pxd $(SAGE_SRC)/sage/libs/meataxe.pxd $(SAGE_SRC)/sage/rings/morphism.pxd | pip matplotlib gap xz $(SAGERUNTIME)