gnu: gst-plugins-base: Update to 1.10.4.

* gnu/packages/gstreamer.scm (gst-plugins-base): Update to 1.10.4.
[source]: Remove obsolete patch 'gst-plugins-base-fix-test-on-32bit.patch'
* gnu/packages/patches/gst-plugins-base-fix-test-on-32bit.patch: Delete file.
* gnu/local.mk (dist_patch_DATA): Remove it.