form_type -> widget_type since IDA 7.7

A minor change is required:

```
  File "C:\Users/User/AppData/Roaming/Hex-Rays/IDA Pro/plugins\HexRaysPyTools\callbacks\scanners.py", line 130, in update
    if ctx.form_type == idaapi.BWN_FUNCS:
Please use "widget_type" instead of "form_type" ("form_type" is kept for backward-compatibility, and will be removed soon.)
```