[webcrypto] Remove a lingering usage of RSA-ES.

LayoutTests/crypto/resources/worker-infinite-loop-generateKey.js

 importScripts('common.js');
 
 function continuouslyGenerateRsaKey()
 {
     var extractable = false;
-    var usages = ['encrypt', 'decrypt'];
+    var usages = ['sign', 'verify'];
     // Note that the modulus length is small.
-    var algorithm = {name: "RSAES-PKCS1-v1_5", modulusLength: 512, publicExponent: hexStringToUint8Array("010001")};
+    var algorithm = {name: "RSASSA-PKCS1-v1_5", modulusLength: 512, publicExponent: hexStringToUint8Array("010001"), hash: {name: 'sha-1'}};
 
     return crypto.subtle.generateKey(algorithm, extractable, usages).then(function(result) {
         // Infinite recursion intentional!
         return continuouslyGenerateRsaKey();
     });
 }
 
 // Starts a Promise which continually generates new RSA keys.
 var unusedPromise = continuouslyGenerateRsaKey();
 
 // Inform the outer script that the worker started.
 postMessage("Worker started");