Move incorrectly placed closing curly brace of `extern "C"` block (#87853)
### Bug description
When `__SYCL_DEVICE_ONLY__` is defined, while building PyTorch, the output of the preprocessing step would not have the closing curly brace of the `extern "C"` block, as it has been incorrectly placed. Compilers don't seem to report an error or a warning for a missing closing brace of an `extern "C"` block.
### Impact of the bug
If `c10/macros/Macros.h` would be included in a C++ file, and after the preprocessing stage, if the preprocessed source file would have some templated code after `extern "C" {`, then, after compilation, linking might fail with the error `templates must have c++ linkage`). eg. https://stackoverflow.com/questions/61717819/template-with-c-linkage-error-when-using-template-keyword-in-main-cpp/61717908#61717908 (its answer also has a small snippet of code to reproduce such an issue).
### Solution in this PR
one-liner bug fix that rectifies the placement of closing curly brace (`}`), so that the `extern "C"` block ends properly when `__SYCL_DEVICE_ONLY__` is defined.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87853
Approved by: https://github.com/jgong5, https://github.com/kit1980, https://github.com/malfet
