remove use of eval() / Function() which was making web3.js incompatib…

…le with Content Security Policy, Trusted Types and other XSS prevention measures

packages/web3-core-requestmanager/src/givenProvider.js

@@ -28,7 +28,7 @@ var givenProvider = null;
 /* jshint ignore:start */
 var global;
 try {
-  global = Function('return this')();
+  global = function() { return this };
 } catch (e) {
   global = window;
 }