swift-format-ignore in conditionally-compiled code results in an assertion failure in PrettyPrint.swift

[a7medev]

When running a debug build of swift-format on a file with the following content:

#if FOO
// swift-format-ignore
print("Hi")
#endif

swift-format crashes with the following assertion failure:

SwiftFormat/PrettyPrint.swift:720: Assertion failed: Too many unresolved delimiter token lengths.

I tested this on a new build from main (commit 80bcc35).