Update rush-plugins/rush-http-build-cache-plugin/README.md

Co-authored-by: Ian Clanton-Thuon <[email protected]>

Author: elliot-nelson

rush-plugins/rush-http-build-cache-plugin/README.md

@@ -28,7 +28,7 @@ Once enabled, configure the HTTP build cache in config file `common/config/rush-
 
 - url: The server to store cache objects.
 - tokenHandler: A script that can print the Authorization header expected by the server. The value printed to `stdout` by this command should be an exact header, for example, `Bearer ab98d8c878d937290d979a9097c90dfffff` or `Basic 098abc7dff==`.
-- isCacheWriteAllowed: A flag that determines if the plugin should write to the cache.
+- `isCacheWriteAllowed`: A flag that determines if the plugin should write to the cache.
 
 ## HTTP Cache Server Requirements