docs: Use the correct libhandy package name

When switching to libhandy 1.0, we accidentally broke the valadoc build,
since that tried looking for the `handy 0.0` package. Fix the custom
target to look for the correct one now.

Fixes https://gitlab.gnome.org/GNOME/gnome-contacts/-/issues/177

(cherry picked from commit 03efda10)

docs/meson.build

@@ -24,7 +24,7 @@ custom_target('docs',
     '--pkg=folks',
     '--pkg=folks-eds',
     '--pkg=libedataserverui-1.2',
-    '--pkg=libhandy-0.0',
+    '--pkg=libhandy-1',
     '--pkg=custom',
     '--pkg=config',
     '--directory=@OUTDIR@',