doc/manual: Remove gitignore file in otherwise empty directory.

I added this by mistake some time ago.  It's not useful.

diff --git a/doc/manual/.gitignore b/doc/manual/.gitignore
deleted file mode 100644 (file)
index 524b61e..0000000
--- a/doc/manual/.gitignore
+++ /dev/null
@@ -1,5 +0,0 @@
-pspp.dvi.gz
-pspp.info.tar.gz
-pspp.pdf
-pspp.txt
-pspp.txt.gz