Fix broken link

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
index 94fb020..50a4901 100644
--- a/.github/pull_request_template.md
+++ b/.github/pull_request_template.md
@@ -14,6 +14,6 @@
 
 ## Notes for the submitter
 
-Please refer to the [contributing guidelines](../CONTRIBUTING.md), especially the
+Please refer to the [contributing guidelines](https://github.com/Mbed-TLS/mbedtls/blob/development/CONTRIBUTING.md), especially the
 checklist for PR contributors.