Update guideline/static-context-provider.md

Co-authored-by: Lukas Reining <lukas.reining@codecentric.de>
Signed-off-by: Thomas Poignant <thomas.poignant@gmail.com>
Signed-off-by: Thomas Poignant <thomas.poignant@gofeatureflag.org>

guideline/static-context-provider.md

@@ -56,7 +56,7 @@ flowchart TD
 ## Polling
 The polling system will make a POST request periodically to the `/ofrep/v1/evaluate/flags` endpoint to check if there is a change in the flags evaluation to be able to store it.
 
-If an `ETag` is available we should always add the header `If-None-Match` with the `ETag` value.
+If an `ETag` of a former evaluation is available we should always add the header `If-None-Match` with the `ETag` value.
 - If the cache is still up-to-date we will receive a `304` telling us that the nothing has changed on the flag management system side.
 - If the cache is outdated we will receive a `200` with the new values of all the flags. In that situation we should:
   1. Replace the actual local cache of flags evaluations.