qmlls: invalid completion inside of for-statements

Currently, when you use the for-statement snippet, autocompleting a let-statement inside the for statement:

for (<autocomplete the let-statement-snippet here>;;) {}

You end up with an extra semicolon:

for (let i = 0;;;) {}

that is inserted after the let-statement template. I thought that I had already fixed the bug, but it seems that the fix is not working:

fix this by using the QQmlLSUtilsAppendOption enum in suggestVariableDeclarationStatementCompletion used by suggestJSStatementCompletion()!