Fix 500 on docx downloading

[2021-04-27T06:33:16.448Z] | prozorro_sale.protocol_service.errors | ERROR - Unknown error caught in API - Package not found at '/protocol_service/prozorro_sale/protocol_service/templates/timber/english/doc/unsuccessful.docx' | X-Request-ID: 15afb1b2afd1b72000829052f8ce27fb
Traceback (most recent call last):
  File "/protocol_service/prozorro_sale/protocol_service/errors.py", line 84, in request_errors_middleware
    return await handler(request)
  File "/protocol_service/prozorro_sale/protocol_service/api.py", line 128, in get_protocol_word
    body=builder.protocol_word(),
  File "/protocol_service/prozorro_sale/protocol_service/protocol_builder.py", line 83, in protocol_word
    doc = DocxTemplate(self.template_path)
  File "/usr/local/lib/python3.9/site-packages/docxtpl/__init__.py", line 38, in __init__
    self.docx = Document(docx)
  File "/usr/local/lib/python3.9/site-packages/docx/api.py", line 25, in Document
    document_part = Package.open(docx).main_document_part
  File "/usr/local/lib/python3.9/site-packages/docx/opc/package.py", line 128, in open
    pkg_reader = PackageReader.from_file(pkg_file)
  File "/usr/local/lib/python3.9/site-packages/docx/opc/pkgreader.py", line 32, in from_file
    phys_reader = PhysPkgReader(pkg_file)
  File "/usr/local/lib/python3.9/site-packages/docx/opc/phys_pkg.py", line 30, in __new__
    raise PackageNotFoundError(
docx.opc.exceptions.PackageNotFoundError: Package not found at '/protocol_service/prozorro_sale/protocol_service/templates/timber/english/doc/unsuccessful.docx'