Harcode RelayHub address into GSNContext

contracts/drafts/meta-tx/GSNContext.sol

@@ -7,15 +7,7 @@ import "./Context.sol";
  * the actual sender and call data from the received values.
  */
 contract GSNContext is Context {
-    address private _relayHub;
-
-    constructor(address relayHub) internal {
-        _setRelayHub(relayHub);
-    }
-
-    function _setRelayHub(address relayHub) internal {
-        _relayHub = relayHub;
-    }
+    address private _relayHub = 0x537F27a04470242ff6b2c3ad247A05248d0d27CE;
 
     // Currently required by the RelayProvider
     function getHubAddr() public view returns (address) {

contracts/mocks/GSNContextMock.sol

@@ -6,9 +6,6 @@ import "../drafts/meta-tx/IRelayRecipient.sol";
 
 // By inheriting from GSNContext, the internal functions are overridden automatically
 contract GSNContextMock is ContextMock, GSNContext, IRelayRecipient {
-    constructor(address relayHub) public GSNContext(relayHub) {
-    }
-
     function acceptRelayedCall(
         address,
         address,

contracts/mocks/GSNRecipientSignedDataMock.sol

@@ -3,10 +3,7 @@ pragma solidity ^0.5.0;
 import "../drafts/meta-tx/GSNRecipientSignedData.sol";
 
 contract GSNRecipientSignedDataMock is GSNRecipientSignedData {
-    constructor(address trustedSigner, address relayHub)
-    public
-    GSNRecipientSignedData(trustedSigner)
-    GSNContext(relayHub) { }
+    constructor(address trustedSigner) public GSNRecipientSignedData(trustedSigner) { }
 
     event MockFunctionCalled();