Improve comments, enhance readability in FCFSScheduling.java

[Hardvan]

The comment improvements for the FCFSScheduling class provide clear and concise explanations of the non-preemptive First Come First Serve (FCFS) scheduling algorithm. The class-level documentation describes how processes are executed in the order they arrive, establishing a solid context for users. Each method is accompanied by detailed comments outlining its purpose, input parameters, and the steps taken, such as calculating waiting and turnaround times. Inline comments within the methods further clarify key operations and logic, enhancing code readability and maintainability while ensuring compliance with Java documentation standards.

• [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 code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 52.29%. Comparing base (7f60d57) to head (a957878).

Files with missing lines	Patch %	Lines
...a/com/thealgorithms/scheduling/FCFSScheduling.java	83.33%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #5500   +/-   ##
=========================================
  Coverage     52.28%   52.29%           
- Complexity     3256     3257    +1     
=========================================
  Files           525      525           
  Lines         15185    15185           
  Branches       2887     2887           
=========================================
+ Hits           7940     7941    +1     
  Misses         6920     6920           
+ Partials        325      324    -1     

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[siriak]

This is not needed, the comments just duplicate what's already written in code