compat: remove glibcxx sanity checks

These checks were added in #4339, (see also #4081), to test
our back-compat stubs, however, those stubs no-longer exist (#22930),
meaning that these checks are now just testing some specific standard
library behaviour, without a particular rationale, or reason, compared
to any other standard library functions we use.

There has also been some discussion about the sanity checks in the
context of the libbitcoinkernel refactoring, see
https://github.com/bitcoin/bitcoin/pull/25065#discussion_r880668218.
Removing the checks removes the need to worry about atleast the glibcxx
checks.

Also remove the list of check from the doc in init.h, because it is
incomplete, and anyone who wants to know what checks are included can
look at the function.

src/init.h

@@ -43,7 +43,7 @@ bool AppInitBasicSetup(const ArgsManager& args);
  */
 bool AppInitParameterInteraction(const ArgsManager& args, bool use_syscall_sandbox = true);
 /**
- * Initialization sanity checks: ecc init, sanity checks, dir lock.
+ * Initialization sanity checks.
  * @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, AppInitParameterInteraction should have been called.
  */