The pythonLocation environment variable is shown as invalid access in this context

### **Describe the bug**
When using the `pythonLocation` environment variable set by the `actions/setup-python` action, this extension reports "Context access might be invalid" even though it is a valid environment variable documented in the official setup-python action.

### **To Reproduce**
Steps to reproduce the behavior:

1. With this workflow:

```yaml
name: Test Workflow

on:
workflow_dispatch:

jobs:
test:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- uses: actions/setup-python@v5
with:
python-version: '3.12'
- name: Cache pip
uses: actions/cache@v4
with:
path: ${{ env.pythonLocation }}/.cache/pip
key: python-${{ hashFiles('setup.py', 'pyproject.toml') }}
```

2. Open the "Problems" panel in VS Code.

3. See the error:
```
Context access might be invalid: pythonLocation
```

### **Expected behavior**
The `pythonLocation` environment variable, which is documented and valid when using `actions/setup-python`, should be recognized properly by this extension.

### **Screenshots**
If applicable, include screenshots of the warning in the Problems panel.

### **Extension Version**
`vX.Y.Z`

### **Additional context**
- Official documentation for the `pythonLocation` variable: [[setup-python environment variables](https://github.com/actions/setup-python#outputs-and-environment-variables)](https://github.com/actions/setup-python#outputs-and-environment-variables).
- This warning is a false positive, as the workflow executes without issues and the variable is set correctly.
- Is this a bug or a limitation of the extension?

---

Beginne damit, die Warnung aus dem im Issue gezeigten Workflow zu reproduzieren, und untersuche die in VS Code im Bereich Problems gemeldete Diagnose. Verfolge, wie die Erweiterung den Zugriff auf den Kontext von Umgebungsvariablen validiert. Als abgeschlossen gilt die Aufgabe, wenn die dokumentierte Verwendung von pythonLocation keine False-Positive-Warnung mehr erzeugt und der Workflow weiterhin gültig ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.