remove incorrect deprecated feature for vcs_tag

In commit 06481666f4 this warning got
moved from build.py to the interpreter. Unfortunately it got added to
the wrong function... it is supposed to be part of custom_target and
even mentions this as the feature_name.

Since then, build_always became a KwargInfo and has the deprecated-since
attribute baked into it. But it didn't have the additional message which
it really should have.

Add that message at the same time we remove it from vcs_tag.

mesonbuild/interpreter/interpreter.py

@@ -1655,8 +1655,6 @@ external dependencies (including libraries) must go to "dependencies".''')
             raise InterpreterException('Unknown target_type.')
 
     @permittedKwargs({'input', 'output', 'fallback', 'command', 'replace_string'})
-    @FeatureDeprecatedKwargs('custom_target', '0.47.0', ['build_always'],
-                             'combine build_by_default and build_always_stale instead.')
     @noPosargs
     def func_vcs_tag(self, node, args, kwargs):
         if 'input' not in kwargs or 'output' not in kwargs:

mesonbuild/interpreter/type_checking.py

@@ -285,6 +285,7 @@ CT_BUILD_BY_DEFAULT: KwargInfo[T.Optional[bool]] = KwargInfo('build_by_default',
 CT_BUILD_ALWAYS: KwargInfo[T.Optional[bool]] = KwargInfo(
     'build_always', (bool, NoneType),
      deprecated='0.47.0',
+     deprecated_message='combine build_by_default and build_always_stale instead.',
 )
 
 CT_BUILD_ALWAYS_STALE: KwargInfo[T.Optional[bool]] = KwargInfo(