formula_installer: tweak no-bottle error message

Follow up to #10183.

This improves the error message displayed when `formula.pour_bottle?` is
false.

Before:

    ❯ brew install python@3.8
    Error: python@3.8: no bottle available!
    The bottle needs the Apple Command Line Tools to be installed.
      You can install them, if desired, with:
        xcode-select --install
    You can try to install from source with e.g.
      brew install --build-from-source python@3.8
    Please note building from source is unsupported. You will encounter build
    failures with some formulae. If you experience any issues please create pull
    requests instead of asking for help on Homebrew's GitHub, Twitter or any other
    official channels.

After:

    ❯ brew install python@3.8
    Error: python@3.8: the bottle needs the Apple Command Line Tools to be installed.
      You can install them, if desired, with:
        xcode-select --install
    You can try to install from source with e.g.
      brew install --build-from-source python@3.8
    Please note building from source is unsupported. You will encounter build
    failures with some formulae. If you experience any issues please create pull
    requests instead of asking for help on Homebrew's GitHub, Twitter or any other
    official channels.