Fix miscellaneous spec failures for Crystal 1.18

[HertzDevil]

• Makes the specs expect the correct closing ANSI escape sequences, rather than \e[0m all the time (Use proper ANSI reset codes in Colorize crystal-lang/crystal#16052).
• Always enables colorization, since child processes now respect Colorize.on_tty_only! by default (Make Colorize.on_tty_only! the default behavior crystal-lang/crystal#15881).
• Makes a spec expect a single-line block to be printed on a single line as well (Handle properly stringifying single line blocks crystal-lang/crystal#15568).

(I didn't edit the minimum Crystal version in shard.yml)