Slightly shorten an Array.from usage in the SignatureManager class

This should be equivalent to the old code, and besides being ever so slightly shorter I'm also finding it a little bit easier to read at a glance.

web/signature_manager.js

@@ -739,13 +739,9 @@ class SignatureManager {
         .then(async signatures => [
           signatures,
           await Promise.all(
-            Array.from(
-              signatures
-                .values()
-                .map(({ signatureData }) =>
+            Array.from(signatures.values(), ({ signatureData }) =>
               SignatureExtractor.decompressSignature(signatureData)
             )
-            )
           ),
         ]);
       return;