Use violation as part of the key as well, as we use that when compari…

…ng equality

Source/SwiftLintCore/Models/Baseline.swift

@@ -5,7 +5,7 @@ private typealias GroupedViolations = [String: [BaselineViolation]]
 private struct BaselineViolation: Equatable, Codable, Hashable {
     let violation: StyleViolation
     let text: String
-    var key: String { text + violation.reason }
+    var key: String { text + violation.reason + violation.severity.rawValue }
 
     init(violation: StyleViolation, text: String) {
         let location = violation.location
@@ -56,6 +56,8 @@ public struct Baseline: Equatable {
 
     /// Filters out violations that are present in the `Baseline`.
     ///
+    /// Assumes that all violations are from the same file.
+    ///
     /// - parameter violations: The violations to filter.
     /// - Returns: The new violations.
     public func filter(_ violations: [StyleViolation]) -> [StyleViolation] {