FAB-3379 update mkdocs.yml
FAB-3379 update mkdocs.yml

remove app-overview.md document reference from mkdocs.yml file

Change-Id: I1bb33753494f3d6fe5ac07b57801db437556a461
Signed-off-by: rameshthoomu <1e6b86b1c013461e7a60f449583642b87c2b3c3b@gmail.com>

ratnakar-asara/fabric-sdk-node,adityachap/fabric-sdk-node,adityachap/fabric-sdk-node,ratnakar-asara/fabric-sdk-node,ratnakar-asara/fabric-sdk-node,ratnakar-asara/fabric-sdk-node