move submodule backend into api folder

.gitmodules

@@ -2,7 +2,7 @@
 	path = nginx
 	url = https://github.com/lesspass/nginx.git
 [submodule "backend"]
-	path = backend
+	path = api
 	url = https://github.com/lesspass/api.git
 [submodule "core"]
 	path = core

api

@@ -0,0 +1 @@
+Subproject commit 2e256f1757f450e9beeb6f1fdf9e289b7aa140f0

backend

@@ -1 +0,0 @@
-Subproject commit cefd03a31c3ba9868d893487a2c92240f14a5e08