Have issue and PR templates redirect to Mbed TLS

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>

.github/issue_template.md

@@ -1,44 +1,10 @@
-<!--
+We are no longer accepting new issues in this repository
+========================================================
 
-   ************************************** WARNING **************************************
+Mbed Crypto is now maintained as part of Mbed TLS, see
+https://github.com/ARMmbed/mbedtls/issues/3064
 
-   The ciarcom bot parses this header automatically. Any deviation from the 
-   template may cause the bot to automatically correct this header or may result in a 
-   warning message, requesting updates.
-
-   Please ensure that nothing follows the Issue request type section, all 
-   issue details are within the Description section and no changes are made to the 
-   template format (as detailed below).
-
-   *************************************************************************************
-
--->
-
-### Description
-
-<!--
-    Required
-    Add detailed description of what you are reporting.
-    Good example: https://os.mbed.com/docs/latest/reference/workflow.html
-    Things to consider sharing:
-    - What target does this relate to?
-    - What toolchain (name + version) are you using?
-    - What tools (name + version - is it mbed-cli, online compiler or IDE) are you using?
-    - What is the SHA of Mbed OS (git log -n1 --oneline)?
-    - Steps to reproduce. (Did you publish code or a test case that exhibits the problem?)
--->
-
-
-### Issue request type
-
-<!--
-    Required
-    Please add only one X to one of the following types. Do not fill multiple types (split the issue otherwise.)
-    Please note this is not a GitHub task list, indenting the boxes or changing the format to add a '.' or '*' in front
-    of them would change the meaning incorrectly. The only changes to be made are to add a description text under the
-    description heading and to add a 'x' to the correct box.
--->
-    [ ] Question
-    [ ] Enhancement
-    [ ] Bug
+Please open your issue in the mbedtls repository:
+https://github.com/ARMmbed/mbedtls/issues/new
 
+Thanks for your interest in Mbed Crypto!

.github/pull_request_template.md

@@ -0,0 +1,10 @@
+We are no longer accepting new pull requests in this repository
+===============================================================
+
+Mbed Crypto is now maintained as part of Mbed TLS, see
+https://github.com/ARMmbed/mbedtls/issues/3064
+
+Please open your pull request in the mbedtls repository:
+https://github.com/ARMmbed/mbedtls/pulls
+
+Thanks for your interest in Mbed Crypto!