gnu: vigra: Fix 'vigra-config' executable.

This fixes a regression introduced in a82e6faa8b
where 'vigra-config' would lack a usable shebang because no 'python'
executable was available.

* gnu/packages/image.scm (vigra)[inputs]: Change from PYTHON to
PYTHON-WRAPPER.

gnu/packages/image.scm

@@ -1023,7 +1023,7 @@ (define-public vigra
       ("libpng" ,libpng)
       ("libtiff" ,libtiff)
       ("openexr" ,openexr)
-      ("python" ,python)
+      ("python" ,python-wrapper)
       ("python-numpy" ,python-numpy)
       ("zlib" ,zlib)))
    (native-inputs