Fix Number cast in Network plugin

Summary:
Getting the error
```
$ /mnt/btrfs/trunk-hg-fb4a-fbsource-86184178-1580774714/xplat/sonar/node_modules/.bin/tsc --noemit
src/plugins/network/index.tsx(180,59): error TS2349: This expression is not callable.
  Type 'Number' has no call signatures.
  error Command failed with exit code 1.
```

EDIT: This error was a red herring from another commit I was based on. Either way, `Number` is discouraged by the Typescript standard (https://www.typescriptlang.org/docs/handbook/declaration-files/do-s-and-don-ts.html), so let's move these to `number` instead.

Reviewed By: mweststrate

Differential Revision: D19712113

fbshipit-source-id: b754780063a1c429724abcd343da06514671bc83

src/plugins/network/index.tsx

@@ -397,7 +397,8 @@ function calculateState(
   }
 
   rows.sort(
-    (a: TableBodyRow, b: TableBodyRow) => Number(a.sortKey) - Number(b.sortKey),
+    (a: TableBodyRow, b: TableBodyRow) =>
+      (a.sortKey as number) - (b.sortKey as number),
   );
 
   return {