Change files encodings to UTF-8

[sfc-gh-knozderko]

Description

Change files encodings to UTF-8

Checklist

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 87.25183% with 122 lines in your changes are missing coverage. Please review.

Project coverage is 84.66%. Comparing base (14cf8a5) to head (18f5c59).

Files	Patch %	Lines
Snowflake.Data/Core/Session/SFSession.cs	82.55%	58 Missing and 9 partials :warning:
Snowflake.Data/Core/Session/SFSessionProperty.cs	83.73%	37 Missing and 3 partials :warning:
Snowflake.Data/Core/HttpUtil.cs	95.41%	11 Missing and 4 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #927 +/- ## ======================================= Coverage 84.66% 84.66% ======================================= Files 89 89 Lines 9694 9694 Branches 919 919 ======================================= Hits 8207 8207 Misses 1259 1259 Partials 228 228 ```

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