Update README to reflect the updated nix flake

When using the nix flake to launch a development environment, the setup
script for Linux/Mac is no longer needed to create the virtual
environment.

README.md

@@ -202,8 +202,8 @@ _Learn more about setting up a virtual environment [here](https://docs.python.or
 
   - Run the "TagStudio.sh" script, and the program should launch! (Make sure that the script is marked as executable if on Linux). Note that launching from the script from outside of a terminal will not launch a terminal window with any debug or crash information. If you wish to see this information, just launch the shell script directly from your terminal with `./TagStudio.sh`.
 
-  - **NixOS** (TagStudio.sh)
-    - Use the provided `flake.nix` file to create and enter a working environment by running `nix develop`. Then, run the `TagStudio.sh` script.
+  - **NixOS** (Nix Flake)
+    - Use the provided `flake.nix` file to create and enter a working environment by running `nix develop`. Run `python3 tagstudio/tag_studio.py` to launch the program.
 
 - **Any** (No Scripts)