[wallet] [rpc] Remove getlabeladdress RPC

labels are associated with addresses (rather than addresses being
associated with labels, as was the case with accounts). The
getlabeladdress does not make sense in this model, so remove it.

getaccountaddress is still supported for one release as the accounts
API is deprecated.

test/functional/rpc_deprecated.py

@@ -40,7 +40,6 @@ class DeprecatedRpcTest(BitcoinTestFramework):
         #
         # The following 'label' RPC methods are usable both with and without the
         # -deprecatedrpc=accounts switch enabled.
-        # - getlabeladdress
         # - getaddressesbylabel
         # - getreceivedbylabel
         # - listlabels
@@ -69,10 +68,6 @@ class DeprecatedRpcTest(BitcoinTestFramework):
         assert_raises_rpc_error(-32, "getaccountaddress is deprecated", self.nodes[0].getaccountaddress, "label0")
         self.nodes[1].getaccountaddress("label1")
 
-        self.log.info("- getlabeladdress")
-        self.nodes[0].getlabeladdress("label0")
-        self.nodes[1].getlabeladdress("label1")
-
         self.log.info("- getaddressesbyaccount")
         assert_raises_rpc_error(-32, "getaddressesbyaccount is deprecated", self.nodes[0].getaddressesbyaccount, "label0")
         self.nodes[1].getaddressesbyaccount("label1")