Discard newlines when sorting imports.

When the author inserts a newline between the `import` token and the imported path, that newline shouldn't be considered when sorting the paths.

Author: dylansturg

Tests/SwiftFormatPrettyPrintTests/XCTestManifests.swift

@@ -207,9 +207,7 @@ extension DifferentiationAttributeTests {
     //   `swift test --generate-linuxmain`
     // to regenerate.
     static let __allTests__DifferentiationAttributeTests = [
-        ("testDerivative", testDerivative),
         ("testDifferentiable", testDifferentiable),
-        ("testTranspose", testTranspose),
     ]
 }