README.md: remove outdated information

There is some outdated information in the README.md files of
hello-stk and imsi-change.

Related: OS#6069

hello-stk/README.md

@@ -1,8 +1,4 @@
 # Hello World SIM Toolkit Program
 
 This is the source code to a very simple *Hello World* Java SIM Toolkit
-application.  You typically install it using the tools from the
-<http://git.osmocom.org/sim/sim-tools/> repository.
-
-For more information see
-<https://osmocom.org/projects/cellular-infrastructure/wiki/Shadysimpy>
+application.