fix(misconf): make protocol checks case-insensitive

[nikpivkin]

Terraform converts upper case to lower case:

Config:

resource "aws_security_group_rule" "ignored_ingress_22_tcp" {
  cidr_blocks       = ["0.0.0.0/0"]
  description       = "Allow 22/tcp ingress from anywhere."
  from_port         = 22
   to_port           = 22
  protocol          = "TCP"
  security_group_id = "sg-123456"
  type              = "ingress"
}

Plan:

  # aws_security_group_rule.ignored_ingress_22_tcp will be created
  + resource "aws_security_group_rule" "ignored_ingress_22_tcp" {
      + cidr_blocks              = [
          + "0.0.0.0/0",
        ]
      + description              = "Allow 22/tcp ingress from anywhere."
      + from_port                = 22
      + id                       = (known after apply)
      + protocol                 = "tcp"
      + security_group_id        = "sg-123456"
      + security_group_rule_id   = (known after apply)
      + self                     = false
      + source_security_group_id = (known after apply)
      + to_port                  = 22
      + type                     = "ingress"
    }

Discussed in #8459