Replace github.com/llnl/spack with github.com/spack/spack (#6142)

We moved to a new GitHub org! Now make the code and docs reflect that.

templates/modules/modulefile.tcl

@@ -1,5 +1,5 @@
 #%Module1.0
-## Module file created by spack (https://github.com/LLNL/spack) on {{ timestamp }}
+## Module file created by spack (https://github.com/spack/spack) on {{ timestamp }}
 ##
 ## {{ spec.short_spec }}
 ##
@@ -79,4 +79,4 @@ unsetenv {{ cmd.name }}
 
 {% block footer %}
 {# In case he module needs to be extended with custom TCL code #}
-{% endblock %}
+{% endblock %}