chore: remove lnurl wallet and withdraw feature (#2293)

* chore: remove lnurl wallet and withdraw feature
this feature is undocumented and the code is very outdated. i don't think it is worth to keep.
looking at the `/lnurlwallet` endpoint for example, it creates a new user and wallet without even checking if the creation of users is allowed
* remove lnurl callback

---------

Co-authored-by: Arc <33088785+arcbtc@users.noreply.github.com>

lnbits/static/js/base.js

@@ -22,19 +22,12 @@ window.LNbits = {
         data: data
       })
     },
-    createInvoice: async function (
-      wallet,
-      amount,
-      memo,
-      unit = 'sat',
-      lnurlCallback = null
-    ) {
+    createInvoice: async function (wallet, amount, memo, unit = 'sat') {
       return this.request('post', '/api/v1/payments', wallet.inkey, {
         out: false,
         amount: amount,
         memo: memo,
-        unit: unit,
-        lnurl_callback: lnurlCallback
+        unit: unit
       })
     },
     payInvoice: function (wallet, bolt11) {