abi tests: from 'char' from the _Generic in PRINT_CONSTANT

We already have signed and unsigned char, so char is a duplicate
and fails on MSVC

Author: pbor

src/codegen/sys/tests.rs

@@ -275,7 +275,6 @@ fn generate_constant_c(
 #define FORMAT_CONSTANT(CONSTANT_NAME) \
     _Generic((CONSTANT_NAME), \
         char *: "%s", \
-        const char *: "%s", \
         signed char: "%hhd", \
         unsigned char: "%hhu", \
         short int: "%hd", \