Fixed some typos in documentation

[wakaree]

Description

I found 2 issues in documentation and fixed it:

• In the i18n LazyProxy usage example, there was a comparison of the lowercase text with "My menu entry".
• The bound_filter parameter has been removed from the TelegramEventObserver filter method, so this parameter should not be in the docstring.

Type of change

• Documentation (typos, code examples or any documentation update)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[github-actions]

✔️ Changelog found.

Thank you for adding a description of the changes

[codecov]

Codecov Report

Merging #1268 (74eee59) into dev-3.x (8ff992b) will not change coverage.
Report is 1 commits behind head on dev-3.x.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           dev-3.x     #1268   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          364       364           
  Lines         9313      9313           
=========================================
  Hits          9313      9313           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

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Files Changed	Coverage Δ
aiogram/dispatcher/event/telegram.py	100.00% <ø> (ø)