Address review feedback from @keith-hall: wrap the abbreviation
removal instructions in a GitHub callout (> [!TIP]) to visually
separate them from the main setup flow. Also reorder so the
'This way, you can keep on using...' sentence follows directly
after the abbreviation creation, improving readability.
Add documentation showing how to erase the fish abbreviations for
--help and -h, since the dash-prefixed names make removal non-obvious.
The key is using -- before the abbreviation name to prevent fish from
interpreting it as a flag.
Closes#3536