json-glib.wrap: pin to 1.6.0 tag
Newer than the 1.4 branch, and circumvents a bug in the docs/meson.build file on Windows ("Method 'get_pkgconfig_variable()' is invalid for an internal dependency").
Newer than the 1.4 branch, and circumvents a bug in the docs/meson.build file on Windows ("Method 'get_pkgconfig_variable()' is invalid for an internal dependency").