[gnome-photos] flatpak: Don't use a non-existent build flag

[Debarshi Ray <debarshir src gnome org>]

commit 993018a3c7e3168f8657aecef8060937c1da96dc
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Sep 26 08:51:43 2018 +0200

    flatpak: Don't use a non-existent build flag
    
    There has never ever been a --disable-documentation build flag, yet,
    somehow it has been present in the Flatpak manifest since it was first
    added to the gnome-apps-nightly repository.
    
    GNOME Online Accounts has a --disable-documentation flag to disable
    generating the man page for goa-daemon(8), which is already covered by
    the --disable-backend flag. So, it might have been a typo while writing
    the manifest.

 flatpak/org.gnome.Photos.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/flatpak/org.gnome.Photos.json b/flatpak/org.gnome.Photos.json
index 2eca6eb5..c2fb9948 100644
--- a/flatpak/org.gnome.Photos.json
+++ b/flatpak/org.gnome.Photos.json
@@ -295,7 +295,7 @@
         },
         {
             "name": "gnome-photos",
-            "config-opts": [ "--disable-documentation", "--disable-Werror" ],
+            "config-opts": [ "--disable-Werror" ],
             "sources": [
                 {
                     "type": "git",