gnu: Remove unneeded 'imported-modules' fields for 'origin'.

* gnu/packages/engineering.scm (fastcap)[source](modules,
imported-modules): Remove.
* gnu/packages/wm.scm (awesome)[source](imported-modules): Remove.
* tests/packages.scm ("package-source-derivation, snippet"): Remove
'imported-modules' field.

gnu/packages/engineering.scm

@@ -229,10 +229,6 @@ optimizer; and it can produce photorealistic and design review images.")
               (snippet
                ;; Remove a non-free file.
                '(delete-file "doc/psfig.sty"))
-              (modules '((guix build utils)
-                         (guix build download)
-                         (guix ftp-client)))
-              (imported-modules modules)
               (patches (search-patches "fastcap-mulSetup.patch"
                                        "fastcap-mulGlobal.patch"))))
     (build-system gnu-build-system)

gnu/packages/wm.scm

@@ -393,7 +393,6 @@ experience.")
                "1m910lr7wkw2dgzmirfvz7dasfswhhccdf65l21iiciv24c3w1bb"))
              (modules '((guix build utils)
                         (srfi srfi-19)))
-             (imported-modules '((guix build utils)))
              (snippet
               ;; Remove non-reproducible timestamp and use the date of the
               ;; source file instead.

tests/packages.scm

@@ -335,7 +335,6 @@
                        ("patch" ,%bootstrap-coreutils&co)))
                     (patch-guile %bootstrap-guile)
                     (modules '((guix build utils)))
-                    (imported-modules modules)
                     (snippet '(begin
                                 ;; We end up in 'bin', because it's the first
                                 ;; directory, alphabetically.  Not a very good