How do I unset or get rid of a bash function?

The unset built-in command takes an option, -f, to delete functions:

unset -f foo

Form the unset entry in the bash manpage:

If -f is specified, each name refers to a shell function, and the function definition is removed.

Note: -f is only really necessary if a variable with the same name exists. If you do not also have a variable named foo, then unset foo will delete the function.

See help unset:

unset: unset [-f] [-v] [-n] [name ...]

Unset values and attributes of shell variables and functions.

For each NAME, remove the corresponding variable or function.

Options:
  -f    treat each NAME as a shell function
  -v    treat each NAME as a shell variable
  -n    treat each NAME as a name reference and unset the variable itself
    rather than the variable it references

Without options, unset first tries to unset a variable, and if that fails,
tries to unset a function.

Some variables cannot be unset; also see `readonly'.

Exit Status:
Returns success unless an invalid option is given or a NAME is read-only.

There is neither unset --help nor man unset unfortunately.