posix: profiles: remove duplicate Kconfig option

Remove the duplicate Kconfig option `CONFIG_POSIX_SYSTEM_INTERFACES` in
`lib/posix/Kconfig.profile` that shadows the option in
`lib/posix/Kconfig`.

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

lib/posix/Kconfig.profile

@@ -2,12 +2,6 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-config POSIX_SYSTEM_INTERFACES
-	bool
-	select NATIVE_LIBC_INCOMPATIBLE
-	help
-	  Make POSIX headers available to the system without the "zephyr/posix" prefix.
-
 config POSIX_API
 	bool "POSIX APIs"
 	select POSIX_SYSTEM_INTERFACES