doc/Makefile.am: Fix `clean` target

The `doc/Vorbis_I_spec*.png` files are checked into git, but were also
being incorrectly deleted during `make clean` because they were listed
in `CLEANFILES`.

diff --git a/doc/Makefile.am b/doc/Makefile.am
index 1745901..5dfbccf 100644 (file)
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -77,7 +77,6 @@ CLEANFILES = $(SPEC_TEX:%.tex=%.aux) \
             Vorbis_I_spec.lg  Vorbis_I_spec.log \
             Vorbis_I_spec.out Vorbis_I_spec.tmp \
             Vorbis_I_spec.toc Vorbis_I_spec.xref \
-            Vorbis_I_spec*.png \
             zzVorbis_I_spec.ps
 DISTCLEANFILES = $(built_docs)