manual: don't define fig-bsc twice

Change-Id: Ibaed44a8de5425b420820a13f14c92c38b9c5fd9
diff --git a/doc/manuals/chapters/overview.adoc b/doc/manuals/chapters/overview.adoc
index 0b93617..9251a7c 100644
--- a/doc/manuals/chapters/overview.adoc
+++ b/doc/manuals/chapters/overview.adoc
@@ -52,7 +52,7 @@
 }
 ----
 
-[[fig-bsc]]
+[[fig-bsc-e1]]
 .Integration of legacy E1 BTS in AoIP network
 [graphviz]
 ----