libc/stdio: Remove wchar_t functions from NEWLIB_NANO_FORMATTED_IO

Regression tested in basepoints/gcc-14-9032-g945cb8490cb with arm-none-eabi.

Example failure without this change:
$ arm-none-eabi-g++ .../pr100611.C -std=c++20 --specs=nosys.specs -o /dev/null --specs=nano.specs
.../ld: .../libc_nano.a(libc_a-svfwprintf.o): in function `_svfwprintf_r':
(.text._svfwprintf_r+0xd8): undefined reference to `__ssputws_r'
.../ld: (.text._svfwprintf_r+0x834): undefined reference to `__ssputws_r'
.../ld: (.text._svfwprintf_r+0x85c): undefined reference to `__ssputws_r'
.../ld: (.text._svfwprintf_r+0x8a8): undefined reference to `__ssputws_r'
.../ld: (.text._svfwprintf_r+0x8dc): undefined reference to `__ssputws_r'
.../ld: .../libc_nano.a(libc_a-svfwprintf.o):(.text._svfwprintf_r+0x900): more undefined references to `__ssputws_r' follow
collect2: error: ld returned 1 exit status

Signed-off-by: Torbjörn SVENSSON <[email protected]>
Co-authored-by: Yvan ROUX <[email protected]>