modify docs to utilize backend:requests

doc/man/salt.7

@@ -44946,7 +44946,7 @@ set in the master\(aqs configuration file:
 .sp
 .nf
 .ft C
-requests_lib: True
+backend: requests
 .ft P
 .fi
 .UNINDENT
@@ -232679,7 +232679,7 @@ my\-rest\-api:
     url: https://api.github.com/
   keys:
     url: https://api.github.com/users/{{user}}/keys
-    requests_lib: True
+    backned: requests
 .ft P
 .fi
 .UNINDENT

doc/topics/cloud/azure.rst

@@ -710,7 +710,7 @@ set in the master's configuration file:
 
 .. code-block:: bash
 
-    requests_lib: True
+    backend: requests
 
 The following functions are available.
 

salt/sdb/rest.py

@@ -22,7 +22,7 @@ requires very little. In the example:
         url: https://api.github.com/
       keys:
         url: https://api.github.com/users/{{user}}/keys
-        requests_lib: True
+        backend: requests
 
 The ``driver`` refers to the REST module, and must be set to ``rest`` in order
 to use this driver. Each of the other items inside this block refers to a