Revert "Benchmarks: suppress rule"

This reverts commit 7ba5ca4.
Suppression is no longer needed because Benchmarks project has
`[<EntryPoint>]` attribute which is now properly recognized.

Author: webwarrior-ws

tests/FSharpLint.Benchmarks/Benchmark.fs

@@ -8,7 +8,6 @@ open FSharpLint.Application.Lint
 open FSharpLint.Framework
 open FSharpLint.Framework.Utilities
 
-// fsharplint:disable NoAsyncRunSynchronouslyInLibrary
 type Benchmark () =
 
     let generateAst source sourceFile =