Fix grammar in declarative container documentation

[okotdaniel]

Description
There's a small grammatical error in the sentence:

"The declarative container can not have any methods or any other attributes then providers."

Problem

"can not" should be written as "cannot" (standard form).

"then" should be "than" (comparison, not sequence).

Optional style improvement: consider making the sentence clearer and more natural.

Proposed Fix
Update the sentence to:

"A declarative container cannot have any methods or attributes other than providers."

This change improves grammar, readability, and formality.

Additional Context
If this is in a .md, .rst, or code docstring file, I can make a small pull request to fix it.

I found this wile on this page:
https://python-dependency-injector.ets-labs.org/containers/declarative.html

[okotdaniel]

I would like to work on this issue.

[ZipFile]

Thanks! You're looking for docs/containers/declarative.rst. Please, make a PR.