Fix Russian translation

[rlz]

Current translation in Russian says 'Agile-manifesto of software development'

Which is completely wrong according to this talk

Changed it to correct 'Manifesto for agile...'

[alex-feel]

Despite the proposed translation seeming more correct at first glance, I oppose this change for the following reasons:

1. Translating "Agile" as "гибкий" does not fully capture the essence of the word. Unfortunately, there is no complete equivalent in Russian.
2. The current translation has already taken root in the community and holds historical value. Moreover, the original translation is widely used in Russian-language sources, and changing it might lead to confusion.
3. The phrase "Agile Manifesto" ("Agile-манифест" in Russian) is correct, as the creators of the manifesto themselves use this phrase on the history page of its creation at https://agilemanifesto.org/history.html (look at the page title, which reads as "History: The Agile Manifesto").

Collectively, these reasons outweigh the "correctness" of the proposed translation.