feat : new dp algo added `UniqueSubsequenceCount.java`

[Tuhinm2002]

• [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 88.88889% with 2 lines in your changes missing coverage. Please review.

Project coverage is 58.19%. Comparing base (0b86774) to head (a505357).

Files with missing lines	Patch %	Lines
...ms/dynamicprogramming/UniqueSubsequencesCount.java	88.88%	2 Missing :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5586      +/-   ##
============================================
+ Coverage     58.17%   58.19%   +0.02%     
- Complexity     3687     3692       +5     
============================================
  Files           548      549       +1     
  Lines         15832    15850      +18     
  Branches       3012     3015       +3     
============================================
+ Hits           9210     9224      +14     
- Misses         6230     6233       +3     
- Partials        392      393       +1     

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[Tuhinm2002]

@alxkm hey check the changes and review it

[Tuhinm2002]

@alxkm check the new code for review