fix(file_handler): avoid writing extra newline character

[ReenigneArcher]

Description

When developing unit tests in #1603, it was discovered that the read_file function would add an extra newline character.

Todo:

• parametrize test to cover more cases

Screenshot

Issues Fixed or Closed

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

LizardByte requires that branches be up-to-date before merging. This means that after any PR is merged, this branch
must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 7.00%. Comparing base (6674090) to head (4cf10c8).

Additional details and impacted files

@@            Coverage Diff             @@
##           nightly   #2335      +/-   ##
==========================================
- Coverage     7.02%   7.00%   -0.03%     
==========================================
  Files           87      87              
  Lines        17675   17670       -5     
  Branches      8395    8391       -4     
==========================================
- Hits          1242    1237       -5     
- Misses       13709   13739      +30     
+ Partials      2724    2694      -30     

Flag	Coverage Δ
Linux	5.35% <100.00%> (-0.02%)	⬇️
Windows	2.56% <100.00%> (-0.05%)	⬇️
macOS-12	7.99% <0.00%> (-0.04%)	⬇️
macOS-13	7.90% <0.00%> (-0.04%)	⬇️
macOS-14	8.25% <0.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/file_handler.cpp	78.57% <100.00%> (-5.64%)	⬇️

... and 23 files with indirect coverage changes