docs: add SKIP_DETAILED_ROUTE to final stage

Signed-off-by: Vitor Bandeira <[email protected]>

Author: vvbandeira

docs/user/FlowVariables.md

@@ -425,6 +425,7 @@ configuration file.
 - [PWR_NETS_VOLTAGES](#PWR_NETS_VOLTAGES)
 - [REPORT_CLOCK_SKEW](#REPORT_CLOCK_SKEW)
 - [ROUTING_LAYER_ADJUSTMENT](#ROUTING_LAYER_ADJUSTMENT)
+- [SKIP_DETAILED_ROUTE](#SKIP_DETAILED_ROUTE)
 - [SKIP_REPORT_METRICS](#SKIP_REPORT_METRICS)
 
 ## generate_abstract variables