Simplify path assembly to app folder

pyzebra/app/cli.py

@@ -4,7 +4,7 @@ import sys
 
 
 def main():
-    app_path = os.path.join(os.path.dirname(os.path.abspath(__file__)))
+    app_path = os.path.dirname(os.path.abspath(__file__))
     subprocess.run(["bokeh", "serve", app_path, *sys.argv[1:]], check=True)