Remove dead link to pkg_resources

Signed-off-by: William Woodruff <william@astral.sh>

Author: woodruffw

source/guides/packaging-namespace-packages.rst

@@ -159,8 +159,8 @@ Legacy namespace packages
 
 These two methods, that were used to create namespace packages prior to :pep:`420`,
 are now considered to be obsolete and should not be used unless you need compatibility
-with packages already using this method. Also, :doc:`pkg_resources <setuptools:pkg_resources>`
-has been deprecated.
+with packages already using this method. Also, ``pkg_resources`` has been deprecated
+(and is fully removed in setuptools 82.0.0).
 
 To migrate an existing package, all packages sharing the namespace must be migrated simultaneously.