Remove apidoc .gitignore from version control

Like the top level .gitignore, there's no reason to track this if it's
being generated automatically. It only produces spurious diff changes
that you almost certainly don't want.

apidoc/.gitignore

@@ -1,53 +0,0 @@
-*.lo
-*.o
-.deps
-.libs
-/*.bak
-/*.gcda
-/*.gcno
-/*.orig
-/*.rej
-/*.tab.c
-/*~
-/.*.sw[nop]
-/.dirstamp
-/.gitignore
-/GPATH
-/GRTAGS
-/GSYMS
-/GTAGS
-/ID
-/Makefile
-/Makefile.in
-/TAGS
-/gtkdoc-check.test
-/html
-/html-build.stamp
-/html.stamp
-/ostree-decl-list.txt
-/ostree-decl.txt
-/ostree-undeclared.txt
-/ostree-undocumented.txt
-/ostree-unused.txt
-/ostree.args
-/ostree.hierarchy
-/ostree.interfaces
-/ostree-overrides.txt
-/ostree.pdf
-/ostree.prerequisites
-/ostree.signals
-/ostree.types
-/pdf-build.stamp
-/pdf.stamp
-/scan-build.stamp
-/setup-build.stamp
-/sgml-build.stamp
-/sgml.stamp
-/so_locations
-/tags
-/tmpl
-/tmpl/*.bak
-/tmpl/ostree-unused.sgml
-/xml
-/version.xml
-_libs