Replacing the wrong link with the correct. (#117)

This change replaces the incorrect link in the .MD file with the
correct one.

Signed-off-by: Motkov Kirill <motkov.kirill@gmail.com>

Author: sosiska

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,7 +6,7 @@ Before creating a pull request, please make sure:
 - You have read the guide for contributing
   - See https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
 - You signed all your commits (otherwise we won't be able to merge the PR)
-  - See https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md#sign-your-work
+  - See https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md#certificate-of-origin---sign-your-work
 - You added unit tests for the new functionality
 - You mention in the PR description which issue it is addressing, e.g. "Resolves #123"
 -->