Make stdout sink _get_osfhandle exception message namespace-agnostic

[Copilot]

This addresses the targeted review feedback to update only comment r3353786308. The hard-coded spdlog:: prefix in a stdout_sink_base exception message was made namespace-agnostic to align with SPDLOG_NAMESPACE overrides.

• Change

  • Updated the Windows-path exception text in include/spdlog/sinks/stdout_sinks-inl.h to remove the hard-coded namespace prefix.

• Why this matters

  • Prevents misleading error text when spdlog is compiled under a custom namespace.

// before
throw_spdlog_ex("spdlog::stdout_sink_base: _get_osfhandle() failed", errno);

// after
throw_spdlog_ex("stdout_sink_base: _get_osfhandle() failed", errno);