Update sample.env removing sample value

Signed-off-by: ali <117142933+muhammad-ali-e@users.noreply.github.com>

Author: muhammad-ali-e

sample.env

@@ -2,4 +2,4 @@ LLMWHISPERER_BASE_URL=https://llmwhisperer-api.unstract.com/v1
 LLMWHISPERER_BASE_URL_V2=https://llmwhisperer-api.us-central.unstract.com/api/v2
 LLMWHISPERER_LOG_LEVEL=DEBUG
 LLMWHISPERER_API_KEY=
-WEBHOOK_TEST_URL=https://httpbin.org/post
+WEBHOOK_TEST_URL=