Remove volatile() property modifier

The modifier got deprecated and wasn't actually needed in any of the used cases.

app/components/topbar-account-panel/component.js

@@ -14,7 +14,7 @@ export default Component.extend({
 
   userHasEthereumWallet: computed(function() {
     return isPresent(window.ethereum);
-  }).volatile(),
+  }),
 
   showConnectButton: computed('userHasEthereumWallet',
                               'kredits.hasAccounts', function() {

app/controllers/dashboard/contributions/show.js

@@ -7,6 +7,6 @@ export default Controller.extend({
 
   ipfsGatewayUrl: computed(function() {
     return config.ipfs.gatewayUrl;
-  }).volatile()
+  })
 
 });

app/controllers/dashboard/contributors/show.js

@@ -12,6 +12,6 @@ export default Controller.extend({
 
   ipfsGatewayUrl: computed(function() {
     return config.ipfs.gatewayUrl;
-  }).volatile()
+  })
 
 });