.gitignore: remove too obvious comments

Some .gitignore files have comments like "Generated files",
"Ignore generated files" at the header part, but they are
too obvious.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

sound/oss/.gitignore

@@ -1,3 +1,2 @@
-#Ignore generated files
 pss_boot.h
 trix_boot.h