fixup! software/ors-amarisoft: enb: Move DRB configuration to standalone file

After 8c841ce6 slapos-render-config.py got broken:

    (py3.venv) kirr@deca:~/src/wendelin/slapos/slapos/software/ors-amarisoft$ python slapos-render-config.py
    Traceback (most recent call last):
      File "/home/kirr/src/wendelin/slapos/slapos/software/ors-amarisoft/slapos-render-config.py", line 87, in <module>
        j2render(config, json_params)
      File "/home/kirr/src/wendelin/slapos/slapos/software/ors-amarisoft/slapos-render-config.py", line 34, in j2render
        f.write(r._render().decode())
                ^^^^^^^^^^^
      File "/home/kirr/src/wendelin/slapos/slapos.recipe.template/slapos/recipe/template/jinja2_template.py", line 215, in _render
        return template_object.render(**self.context).encode(self.encoding)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/home/kirr/src/wendelin/venv/py3.venv/lib/python3.11/site-packages/jinja2/environment.py", line 1301, in render
        self.environment.handle_exception()
      File "/home/kirr/src/wendelin/venv/py3.venv/lib/python3.11/site-packages/jinja2/environment.py", line 936, in handle_exception
        raise rewrite_traceback_stack(source=source)
      File "config/gnb.jinja2.cfg", line 586, in top-level template code
        drb_config: "{{ drb_file }}",
    ^^^^^^^^^^^^^^^^^^^^^^^^^
    jinja2.exceptions.UndefinedError: 'drb_file' is undefined

/cc @jhuge, @lu.xu, @xavier_thompson, @Daetalus

software/ors-amarisoft/slapos-render-config.py

@@ -56,6 +56,7 @@ json_params = """{
     "tx_gain": 62,
     "rx_gain": 43,
     "sib23_file": "sib",
+    "drb_file": "drb",
     "slap_configuration": {
         "tap-name": "slaptap9",
         "configuration.default_lte_bandwidth": "10 MHz",