doc: REST API url is /banks, not /bankds

The documentation didn't agree with the code. Let's fix it

Change-Id: I63771c7ecc975435b8b7415ffb5e0a51fb5acef0
Closes: OS#3963
diff --git a/doc/manuals/chapters/remsim-server.adoc b/doc/manuals/chapters/remsim-server.adoc
index e5ab58d..01d24b2 100644
--- a/doc/manuals/chapters/remsim-server.adoc
+++ b/doc/manuals/chapters/remsim-server.adoc
@@ -40,14 +40,14 @@
 
 No other HTTP operation is implemented.
 
-==== /api/backend/v1/bankds
+==== /api/backend/v1/banks
 
 *GET* obtains a JSON list where each element represents one currently
 connected `osmo-remsim-bankd`.
 
 No other HTTP operation is implemented.
 
-==== /api/backend/v1/bankds/:bank_id
+==== /api/backend/v1/banks/:bank_id
 
 *GET* obtains a single JSON object representing one specific currently
 connected `osmo-remsim-bankd`.