Update tests to check for whitespace

Author: natecook1000

Tests/SourceKitLSPTests/FormattingTests.swift

@@ -43,6 +43,7 @@ final class FormattingTests: XCTestCase {
     let edits = try XCTUnwrap(response)
     let formattedSource = apply(edits: edits, to: source)
 
+    XCTAssert(edits.allSatisfy { $0.newText.allSatisfy(\.isWhitespace) })
     XCTAssertEqual(
       formattedSource,
       """
@@ -283,6 +284,7 @@ final class FormattingTests: XCTestCase {
     let edits = try XCTUnwrap(response)
     let formattedSource = apply(edits: edits, to: source)
 
+    XCTAssert(edits.allSatisfy { $0.newText.allSatisfy(\.isWhitespace) })
     XCTAssertEqual(
       formattedSource,
       #"""

Tests/SourceKitLSPTests/OnTypeFormattingTests.swift

@@ -75,14 +75,14 @@ final class OnTypeFormattingTests: XCTestCase {
     let (_, unmarkedSource) = extractMarkers(source)
     let formattedSource = apply(edits: edits, to: unmarkedSource)
 
+    XCTAssert(edits.allSatisfy { $0.newText.allSatisfy(\.isWhitespace) })
     XCTAssertEqual(
       formattedSource,
       """
       func foo() {
           if let SomeReallyLongVar = Some.More.Stuff(), let a = myfunc() {
       }
       }
-
       """
     )
   }