Improve space complexity to O(1) in WordSearch.

[Maryamh12]

• [ x] I have read CONTRIBUTING.md.
• [ x] This pull request is all my own work -- I have not plagiarized it.
• [ x] All filenames are in PascalCase.
• [x ] All functions and variable names follow Java naming conventions.
• [ x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [ x] All new algorithms include a corresponding test class that validates their functionality.
• [ x] All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 79.41%. Comparing base (8bbd090) to head (bf35e74).

Files with missing lines	Patch %	Lines
...ava/com/thealgorithms/backtracking/WordSearch.java	92.85%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7308      +/-   ##
============================================
- Coverage     79.44%   79.41%   -0.03%     
+ Complexity     7061     7060       -1     
============================================
  Files           788      788              
  Lines         23129    23120       -9     
  Branches       4548     4545       -3     
============================================
- Hits          18374    18361      -13     
- Misses         4021     4024       +3     
- Partials        734      735       +1     

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[DenizAltunkapan]

Thank you for the improved implementation - using in-place marking instead of a separate visited array simplifies the code and reduces memory overhead. @Maryamh12