[shellprocess] [contextualprocess] Unneeded module.desc

- C++ modules should have a CMakeLists.txt which does the
   right thing, e.g. calamares_add_plugin() , and don't need
   a textual module.desc

src/modules/contextualprocess/module.desc

@@ -1,5 +0,0 @@
----
-type:      "job"
-name:      "contextualprocess"
-interface: "qtplugin"
-load:      "libcalamares_job_contextualprocess.so"

src/modules/shellprocess/module.desc

@@ -1,5 +0,0 @@
----
-type:      "job"
-name:      "shellprocess"
-interface: "qtplugin"
-load:      "libcalamares_job_shellprocess.so"