SNOW-914532: Fix variable name in ClearAllPoolsAsync

[sfc-gh-ext-simba-lf]

Description

The PR renames the variable to the correct name for ClearAllPoolsAsync

Checklist

• Code compiles correctly
• Code is formatted according to Coding Conventions
• Created tests which fail without the change (if possible)
• All tests passing (dotnet test)
• Extended the README / documentation, if necessary
• Provide JIRA issue id (if possible) or GitHub issue id in PR name

[codecov]

Codecov Report

Merging #804 (4528ac5) into master (64b638c) will increase coverage by 0.12%.
Report is 1 commits behind head on master.
The diff coverage is 55.55%.

@@            Coverage Diff             @@
##           master     #804      +/-   ##
==========================================
+ Coverage   83.45%   83.57%   +0.12%     
==========================================
  Files          89       89              
  Lines        9065     9073       +8     
  Branches      826      827       +1     
==========================================
+ Hits         7565     7583      +18     
+ Misses       1274     1265       -9     
+ Partials      226      225       -1     

Files	Coverage Δ
Snowflake.Data/Core/Session/SessionPool.cs	90.22% <55.55%> (+1.67%)	⬆️

... and 2 files with indirect coverage changes

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