Remove the syscall sandbox

After initially being merged in #20487, it's no-longer clear that an
internal syscall sandboxing mechanism is something that Bitcoin Core
should have/maintain, especially when compared to better
maintained/supported alterantives, i.e firejail.

Note that given where it's used, the sandbox also gets dragged into the
kernel.

There is some related discussion in #24771.

This should not require any sort of deprecation, as this was only ever
an opt-in, experimental feature.

Closes #24771.

src/init.h

@@ -44,7 +44,7 @@ bool AppInitBasicSetup(const ArgsManager& args, std::atomic<int>& exit_status);
  * @note This can be done before daemonization. Do not call Shutdown() if this function fails.
  * @pre Parameters should be parsed and config file should be read, AppInitBasicSetup should have been called.
  */
-bool AppInitParameterInteraction(const ArgsManager& args, bool use_syscall_sandbox = true);
+bool AppInitParameterInteraction(const ArgsManager& args);
 /**
  * Initialization sanity checks.
  * @note This can be done before daemonization. Do not call Shutdown() if this function fails.