CHANGELOG: add full stop, PR's number

Signed-off-by: Giedrius Statkevičius <[email protected]>

Author: GiedriusS

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## master / unreleased
 
-* [CHANGE] The frontend component now does not cache results if it finds a `Cache-Control` header and if one of its values is `no-store`
+* [CHANGE] The frontend component now does not cache results if it finds a `Cache-Control` header and if one of its values is `no-store`. #1974
 * [ENHANCEMENT] metric `cortex_ingester_flush_reasons` gets a new `reason` value: `Spread`, when `-ingester.spread-flushes` option is enabled.
 * [CHANGE] Flags changed with transition to upstream Prometheus rules manager:
   * `ruler.client-timeout` is now `ruler.configs.client-timeout` in order to match `ruler.configs.url`