posix: deprecated: remove new options without deprecation

A few previously deprecated Kconfig options have not yet been
present for 1 release cycle and can (theoretically) just be
removed, without deprecation (see next commit).

* GETENTROPY
* POSIX_CONFSTR
* POSIX_ENV
* POSIX_SYSLOG

For dependency information, please see
https://docs.zephyrproject.org/3.6.0/kconfig.html#kconfig-search



Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>