[gspell] build: fix `make distcheck` with newer gtk-doc version

[Sébastien Wilmet <swilmet src gnome org>]

commit f22493b8407961d88688d8ea772cde035014741a
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Tue Oct 27 21:33:04 2020 +0100

    build: fix `make distcheck` with newer gtk-doc version
    
    There was the following error when running `make distcheck`:
    
    ERROR: files left in build directory after distclean:
    ./docs/reference/gspell-1.0.actions
    
    This should most probably be fixed in gtk-doc itself, for the autotools
    files that it provides. In the meantime, be able to release gspell.
    
    It also adds the file to the .gitignore via git.mk.

 docs/reference/Makefile.am | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/docs/reference/Makefile.am b/docs/reference/Makefile.am
index 3812022..bf9bc34 100644
--- a/docs/reference/Makefile.am
+++ b/docs/reference/Makefile.am
@@ -75,6 +75,7 @@ EXTRA_DIST +=                 \
        intro.xml.in
 
 DISTCLEANFILES =               \
+       $(DOC_MODULE).actions   \
        gspell-docs.xml         \
        intro.xml