[Test] Remove extraneous whitespace

Author: DougGregor

test/attr/typed_throws_availability_osx.swift

@@ -10,6 +10,3 @@ enum MyError: Error {
 @available(macOS 12, *)
 func throwMyErrorBadly() throws(MyError) { }
 // expected-error@-1{{'MyError' is only available in macOS 13 or newer}}
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