There are multiple post going around on this error in my case the problem was caused by missing quotes around the value of provisioningMode. So instead of this:

resource "kubernetes_storage_class" "us-east-1a" {
  metadata {
    name = "us-east-1a"
  }
  storage_provisioner = "efs.csi.aws.com"
  reclaim_policy      = "Retain"
  parameters = {
    provisioningMode = efs-ap
    fileSystemId     = var.us-east-1a-vol
    directoryPerms   = "777"
  }
  mount_options = ["file_mode=0700", "dir_mode=0777", "mfsymlinks", "uid=1000", "gid=1000", "nobrl", "cache=none"]
}

Use this:

resource "kubernetes_storage_class" "us-east-1a" {
  metadata {
    name = "us-east-1a"
  }
  storage_provisioner = "efs.csi.aws.com"
  reclaim_policy      = "Retain"
  parameters = {
    provisioningMode = "efs-ap"
    fileSystemId     = var.us-east-1a-vol
    directoryPerms   = "777"
  }
  mount_options = ["file_mode=0700", "dir_mode=0777", "mfsymlinks", "uid=1000", "gid=1000", "nobrl", "cache=none"]
}