modules/wayland: Change default value of include_core_only to true

The use of wayland-<client|server>.h is discouraged, therefore
change the default value of include_core_only to true.

docs/markdown/Wayland-module.md

@@ -50,7 +50,7 @@ generated = wl_mod.scan_xml(
   client : true,
   server : true,
   public : false,
-  include_core_only : false,
+  include_core_only : true,
 )
 ```
 This function accepts one or more arguments of either string or file type.

mesonbuild/modules/wayland.py

@@ -66,7 +66,7 @@ class WaylandModule(ExtensionModule):
         KwargInfo('public', bool, default=False),
         KwargInfo('client', bool, default=True),
         KwargInfo('server', bool, default=False),
-        KwargInfo('include_core_only', bool, default=False, since='0.64.0'),
+        KwargInfo('include_core_only', bool, default=True, since='0.64.0'),
     )
     def scan_xml(self, state: ModuleState, args: T.Tuple[T.List[FileOrString]], kwargs: ScanXML) -> ModuleReturnValue:
         if self.scanner_bin is None: