Fix invalid const-qualified function pointer in delayimp.cpp (breaks x86 clang-cl build)

[TomJoey]

Summary

• GetProcAddress returns FARPROC (a function pointer). The line
  if (auto const *real = GetProcAddress(...); real != nullptr) in the
  #if defined(_M_IX86) || defined(__i386__) branch of
  DelayLoadFailureHook deduces real as a pointer to a
  const-qualified function type, which isn't a meaningful
  declaration.
• clang-cl rejects this outright when targeting x86 (-m32):

  error: variable 'real' with type 'const auto *' has incompatible
  initializer of type 'FARPROC' (aka 'int (*)() __attribute__((stdcall)))')
  

• This branch is only compiled for _M_IX86/__i386__, and the
  project's own build-windows.yml matrix only builds x64/arm64, so
  the build break was never caught by CI.
• Every other raw pointer in this file (e.g. the LoadLibrary results
  a few lines above, auto *const h = ...) uses auto *const — a
  non-reassignable pointer to non-const data. That's almost certainly
  what was intended here too; real is never reassigned in this
  scope. Switching to that form fixes the x86 clang-cl build without
  changing behavior (MSVC accepted the original spelling as a
  non-conforming extension).

Test plan

• Build-verified: a downstream project (QQMusicEasier) builds this
  file with clang-cl -m32 (-DCMAKE_C_FLAGS=-m32 -DCMAKE_CXX_FLAGS="-m32 /EHsc",
  Ninja, Release, shared) as part of its CI. With this one-line fix
  applied, that CI run compiles and links prism.dll successfully:
  https://github.com/TomJoey/QQMusicEasier/actions/runs/31920480814
  (previous run without the fix failed with the exact error above:
  https://github.com/TomJoey/QQMusicEasier/actions/runs/31920099844)
• This repo doesn't currently build x86 in CI, so this path isn't
  covered automatically — happy to add an x86 job if useful.

[ethindp]

I currently lack the energy of supporting 32-bit platforms given their increasing rarity, but I will merge this PR if the checks pass. Please note that in order for this PR to be merged you must now add your sign-off per the DCO. (I have been implementing these processes so that contributing is smoother and there is less arbitrary-ness about it.)