[#5754] improve(build): Fix rewrite_config.py with the correct shebang line (#5785)

### What changes were proposed in this pull request?

modified:
- __dev/docker/iceberg-rest-server/rewrite_config.py__

Correct the shebang line to specify the correct shell `bash`
```bash
#!/usr/bin/env bash
```
<br>

### Why are the changes needed?

The `env` command should be assigned an interpreter like `bash` or
`python`.
<br>

Fix: #5754 

### Does this PR introduce _any_ user-facing change?

No.
<br>

### How was this patch tested?
Although we usually execute this script with the Python interpreter (for
example: `python rewrite_config.py`) rather than executing it without an
interpreter, with the fix applied, executing this script without an
interpreter will no longer result in a hang.

Author: liuchunhao

dev/docker/iceberg-rest-server/rewrite_config.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env 
+#!/usr/bin/env bash
 # Licensed to the Apache Software Foundation (ASF) under one
 # or more contributor license agreements.  See the NOTICE file
 # distributed with this work for additional information