refactor(inputrc): remove `show-all-if-unmodified` setting
refactor(inputrc): remove `show-all-if-unmodified` setting

It turned out that `set show-all-if-unmodified on` does not give me a
desired result, and also is said that `set show-all-if-ambiguous on`
overrides this option; thus remove it as redundant.

See: https://stackoverflow.com/q/42192384/1334728

shoichiaizawa/dotfiles,shoichiaizawa/dotfiles,shoichiaizawa/dotfiles