Clean export completions

[tbhaxor]

Description

This PR fixes SC2016 in completions/available/export.completion.bash file

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] If my change requires a change to the documentation, I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• [ ] I have added tests to cover my changes, and all the new and existing tests pass.

[tbhaxor]

@NoahGorny @davidpfarrell ping :)

[davidpfarrell]

So not sure where its from (likely brew completions), but I have a much better completion defined in my local:

$ complete -p export

complete -F _export export

$ type _export

_export is a function

_export () 
{ 
    local cur prev words cword;
    _init_completion -n = || return;
    local i action=variable remove=false;
    for ((i = 1; i < cword; i++))
    do
        case ${words[i]} in 
            -p)
                return
            ;;
            -*f*)
                action=function
            ;;&
            -*n*)
                remove=true
            ;;
            -*)
                continue
            ;;
        esac;
        break;
    done;
    if [[ $cur == *=* ]]; then
        local ocur=$cur oprev=$prev;
        prev=${cur%%=*} cur=${cur#*=};
        _variables && return;
        cur=$ocur prev=$oprev;
    fi;
    case $cur in 
        *=)
            local pval=$(quote "$(eval printf %s \"\$\{${cur%=}-\}\")");
            if [[ $pval != \'\' ]]; then
                COMPREPLY=("$pval");
            else
                cur=${cur#*=};
                _filedir;
            fi
        ;;
        *=*)
            cur=${cur#*=};
            _filedir
        ;;
        *)
            if [[ $cword -eq 1 && $cur == -* ]]; then
                COMPREPLY=($(compgen -W '-p $(_parse_usage "$1")' -- "$cur"));
                return;
            fi;
            local suffix="";
            if ! $remove; then
                suffix="=";
                compopt -o nospace;
            fi;
            COMPREPLY=($(compgen -A $action -S "$suffix" -- "$cur"))
        ;;
    esac
}

$ export -<TAB><TAB>
-f  -n  -p  

Regarding the PR:

- complete -o nospace -S = -W '$(printenv | awk -F= "{print \$1}")' export
+ complete -o nospace -S = -W "$(printenv | awk -F= "{print \$1}")" export

The outer ' seems vital as we want to evaluate the printenv later and not now

So it appears to me that we are actually breaking the completion here?