[libhandy] Set "required: false", in build instructions, so meson will use the subproject when dep not found.

[Adrien Plazas <aplazas src gnome org>]

commit baa96007abce3bc7ef658f7824e9c69b1837c366
Author: lorenzo <ranfdev gmail com>
Date:   Sun Jul 12 10:35:30 2020 +0000

    Set "required: false", in build instructions, so meson will use the subproject when dep not found.

 doc/build-howto.xml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/doc/build-howto.xml b/doc/build-howto.xml
index 5e176dcd..c7e967d6 100644
--- a/doc/build-howto.xml
+++ b/doc/build-howto.xml
@@ -72,7 +72,7 @@
     </para>
 
     <informalexample><programlisting>
-      &package_string;_dep = dependency('&package_ver_str;', version: '>= &package_version;')
+      &package_string;_dep = dependency('&package_ver_str;', version: '>= &package_version;', required: 
false)
       if not &package_string;_dep.found()
         &package_string; = subproject(
           '&package_string;',