gnu: khard: Move propagated-inputs to inputs.

As a package one would install we can rely on wrapping the package and
not propagating inputs to make it work correctly.

* gnu/packages/mail.scm (khard)[propagated-inputs]: Move all python
packages ...
[inputs]: ... to here.

gnu/packages/mail.scm

@@ -1977,7 +1977,7 @@ maintained.")
                #t))))))
     (native-inputs
      `(("python-setuptools-scm" ,python-setuptools-scm)))
-    (propagated-inputs
+    (inputs
      `(("python-atomicwrites" ,python-atomicwrites)
        ("python-configobj" ,python-configobj)
        ("python-pyyaml" ,python-pyyaml)