[FIX] CONTRIBUTING.md Dead link fixed

Fix broken url to the Corporate Contributor License Agreement in the
CONTRIBUTING.md

Closes UI5#1498

Change-Id: Iae04a4aad2cfad00d73e5b9c75d3c43fa2bb94d5

Author: mxschmitt

CONTRIBUTING.md

@@ -137,7 +137,7 @@ which can be [found here](https://gist.github.com/CLAassistant/bd1ea8ec8aa035741
 If employees of a company contribute code, in **addition** to the individual agreement above, there needs to be one company agreement submitted. This is mainly for the protection of the contributing employees.
 
 A company representative authorized to do so needs to download, fill, and print
-the [Corporate Contributor License Agreement](https://github.com/SAP/openui5/blob/master/docs/SAP Corporate Contributor License Agreement.pdf) form. Then either:
+the [Corporate Contributor License Agreement](/docs/SAP%20Corporate%20Contributor%20License%20Agreement.pdf) form. Then either:
 
 -   Scan it and e-mail it to [[email protected]](mailto:[email protected]) and [[email protected]](mailto:[email protected])
 -   Fax it to: +49 6227 78-45813