fix(python): avoid FileAlreadyExistsException in venv cleanup (#373)

## Summary

- Remove redundant `Files.createFile()` before `Files.write()` in
`PythonControllerVirtualEnv`
- `Files.write()` already creates the file if it doesn't exist
- The `createFile()` call caused `FileAlreadyExistsException` when a
previous analysis failed mid-way and left the `requirements.txt` behind
in `/tmp/trustify_da_env/`

## Test plan

- [x] All existing Python provider tests pass (35 tests, 0 failures)
- [x] Manual: trigger a Python analysis that fails (e.g. unresolvable
dep), then trigger another — should no longer throw
`FileAlreadyExistsException`

Implements [TC-3894](https://redhat.atlassian.net/browse/TC-3894)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Chao Wang <chaowan@redhat.com>

Author: ruromero

src/main/java/io/github/guacsec/trustifyda/utils/PythonControllerVirtualEnv.java

@@ -91,7 +91,6 @@ public void cleanEnvironment(boolean deleteEnvironment) {
         Files.deleteIfExists(envRequirements);
         String freezeOutput =
             Operations.runProcessGetOutput(pythonEnvironmentDir, pipBinaryLocation, "freeze");
-        Files.createFile(envRequirements);
         Files.write(envRequirements, freezeOutput.getBytes());
         Operations.runProcessGetOutput(
             pythonEnvironmentDir, pipBinaryLocation, "uninstall", "-y", "-r", "requirements.txt");