fix: correct frontmatter delimiter in test_write_note_no_tags test

The test had a malformed YAML frontmatter delimiter (-- instead of ---) 
which was causing parsing failures. This fixes the test to use proper 
YAML frontmatter formatting.

Co-authored-by: Paul Hernandez <phernandez@users.noreply.github.com>

Author: claude[bot]

tests/mcp/test_tool_write_note.py

@@ -63,7 +63,7 @@ async def test_write_note_no_tags(app):
     content = await read_note.fn("test/simple-note")
     assert (
         dedent("""
-        --
+        ---
         title: Simple Note
         type: note
         permalink: test/simple-note