Fix flask version for Socket compatibility

[gautierdag]

Current versions of flask break with ai2thor==2.1.0 and give socket errors.

From Player.log:

(Filename: ./Runtime/Export/Debug.bindings.h Line: 45)

SocketException: The socket has been shut down
  at System.Net.Sockets.Socket.Send (System.Byte[] buf) [0x00000] in <filename unknown>:0
  at AgentManager+<EmitFrame>c__Iterator3.MoveNext () [0x00000] in <filename unknown>:0
  at UnityEngine.SetupCoroutine.InvokeMoveNext (IEnumerator enumerator, IntPtr returnValueAddress) [0x00000] in <>

(Filename:  Line: -1)

The solution is to fix flask==2.0.3 and Werzeug==2.0.3 as in #130.

[MarcCote]

Thanks. This was needed for ALFWorld. @MohitShridhar