More typing for connection.

[jettify]

What do these changes do?

Are there changes in behavior for the user?

Related issue number

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> (e.g. 588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the PR
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: Fix issue with non-ascii contents in doctest text files.

[codecov]

Codecov Report

Merging #420 (9630f77) into master (5f81278) will decrease coverage by 0.10%.
The diff coverage is 94.73%.

@@            Coverage Diff             @@
##           master     #420      +/-   ##
==========================================
- Coverage   86.98%   86.88%   -0.10%     
==========================================
  Files           6        6              
  Lines         484      488       +4     
  Branches       73       73              
==========================================
+ Hits          421      424       +3     
- Misses         47       48       +1     
  Partials       16       16              

Impacted Files	Coverage Δ
aioodbc/connection.py	85.21% <94.73%> (-0.30%)	⬇️

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