Update organizational-structure-overview.md

Missed RSTUF

Co-authored-by: Zach Steindler <steiza@github.com>
Signed-off-by: Marcela Melara <marcela.melara@intel.com>

organizational-structure-overview.md

@@ -78,6 +78,7 @@ flowchart TB
         BP ---> BestPracticesBadge[Best Practices Badge]
         MM ---> SecurityInsights[Security Insights]
         MM ---> SecurityMetrics[Security Metrics]
+        REP ---> Rstuf[Repository Service for TUF]
         SCI ---> Gittuf[gittuf]
         SCI ---> GUAC[GUAC]
         SCI ---> S2C2F[S2C2F]