Developers of PCSX2 cannot distribute the BIOS because Sony would immediately issue a takedown. This is why every guide on the official PCSX2 website instructs you to dump your own BIOS.
However, in the modern era of gaming, playing Tekken 4 often involves emulation. Whether due to the scarcity of working PS2 hardware or the desire for upscaling and save states, many turn to software like PCSX2. This is where a specific, critical term enters the search bar: tekken 4 bios