/ Remove all range protections in the spreadsheet that the user has permission to edit.
var ss = SpreadsheetApp.getActive();
var protections = ss.getProtections(SpreadsheetApp.ProtectionType.RANGE);
for (var i = 0; i < protections.length; i++) {
  var protection = protections[i];
  if (protection.canEdit()) {
    protection.remove();
  }
}