Fix link to Lab 5 from Lab 11

Signed-off-by: Frankie Gold <[email protected]>

Author: codegold79

lab11.md

@@ -197,6 +197,6 @@ $ echo -n "This is a message" | faas-cli invoke hmac-protected --sign hmac --key
 HMAC validation failed.
 ```
 
-As a follow-up task you could apply HMAC to secure your endpoint on `issue-bot` from [lab 5](https://github.com/openfaas/workshop/blob/7f1b0246376b7e4380bb5874655f28254c15f749/lab5.md)
+As a follow-up task you could apply HMAC to secure your endpoint on `issue-bot` from [lab 5](https://github.com/openfaas/workshop/blob/master/lab5.md)
 
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