remove_unused_variable incorrect behavior

[otagrua]

remove_unused_variable incorrectly removes unassigned local variables in grouped local assignments after a function call and assigned variable.

Reproduction

a.luau:

local c = 0;
(function()
    local a, b, c = (function()end)(), 0;
    c = 1;
end)();
assert(c == 0);

.darklua.json:

{
    "rules": [
        "remove_unused_variable"
    ]
}

darklua process a.luau out.luau --verbose
 INFO > using configuration file `.darklua.json`
 INFO > successfully processed `a.luau`
 INFO > executed work in 1.2508ms
successfully processed 1 file (in 2.049ms)

darklua --version
darklua 0.13.1

out.luau:

local c = 0;
(function()
local a=(function()end)();
    c = 1;
end)();
assert(c == 0);

This output is incorrect. When combined with group_local_assignment and rename_variables, this bug is more likely to break scripts.