Update src/content/docs/workers/wrangler/system-environment-variables.mdx

Co-authored-by: Pete Bacon Darwin <[email protected]>

Author: CarmenPopoviciu

src/content/docs/workers/wrangler/system-environment-variables.mdx

@@ -74,7 +74,7 @@ Wrangler supports the following environment variables:
 
 * `WRANGLER_HTTPS_KEY_PATH` <Type text="string" /> <MetaInfo text="optional" />
 
-  * Path to a custom certificate key.
+  * Path to a custom HTTPS certificate key when running `wrangler dev`, to be used with `WRANGLER_HTTPS_CERT_PATH`.
 
 * `WRANGLER_HTTPS_CERT_PATH` <Type text="string" /> <MetaInfo text="optional" />