debugpy: Fix the EXE001 shebangs on the three top-level scripts.

`ruff check .` reports EXE001 on all three, and the rule is pointing at
a real inconsistency rather than a style preference.

`demo.py` and `test_vscode.py` are run as `micropython demo.py`, so
`#!/usr/bin/env python3` names an interpreter that cannot run them; the
line is removed. `dap_monitor.py` is a host-side CPython tool whose
shebang is correct, so it becomes executable instead.

Claude-Session: https://claude.ai/code
Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

Author: pi-anl

python-ecosys/debugpy/dap_monitor.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 """Simple demo of MicroPython debugpy functionality."""
 
 import sys

python-ecosys/debugpy/demo.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 """Test script for VS Code debugging with MicroPython debugpy."""
 
 import sys