Added SimplePendulumRK4

[the-yash-rajput]

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

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.34884% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.99%. Comparing base (873dd97) to head (c478533).

Files with missing lines	Patch %	Lines
...a/com/thealgorithms/physics/SimplePendulumRK4.java	95.34%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6800      +/-   ##
============================================
+ Coverage     77.96%   77.99%   +0.02%     
- Complexity     6431     6444      +13     
============================================
  Files           736      737       +1     
  Lines         21476    21519      +43     
  Branches       4204     4208       +4     
============================================
+ Hits          16744    16783      +39     
- Misses         4060     4063       +3     
- Partials        672      673       +1     

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[the-yash-rajput]

@alxkm Please review and merge this PR.
Thanks.