schema: Remove dec-or-hex-integer and hex-integer type

schema: Remove dec-or-hex-integer and hex-integer type

Reflect in the schema that hexadecimal values aren't supported in enum
items (and expressions) by removing the 'dec-or-hex-integer' and
'hex-integer' type.

Hexadecimal values are not supported "as some languages have a different
notation for hex-values" and therefor such hexadecimal values have been
explicitly replaced with decimal values in other commits, see:

    183ecff Replaced hex-values with decimal ones
    8b3c120 did remaining replacements of hex constants with decimal

Signed-off-by: Daniel Martin <consume.noise@gmail.com>