Update docs/querying/functions.md

Signed-off-by: Julien Pivotto <roidelapluie@o11y.eu>

docs/querying/functions.md

@@ -14,7 +14,7 @@ vector, which if not provided it will default to the value of the expression
 _Notes about the experimental native histograms:_
 
 * Ingesting native histograms has to be enabled via a [feature
-  flag](https://prometheus.io/docs/prometheus/latest/feature_flags/). As long as no native histograms
+  flag](../feature_flags.md#native-histograms). As long as no native histograms
   have been ingested into the TSDB, all functions will behave as usual.
 * Functions that do not explicitly mention native histograms in their
   documentation (see below) will ignore histogram samples.