update palindrome_number.py with string approach

[yashigupta4623]

In this commit, I tried to approach the check for Palindrome number using String approach with Python as the Programming Language.

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  fixes #[issue number that will be closed through this PR]

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Checklist:

• I have placed my code file in the (/Code) Folder e.g. If it's a Code in JAVA then I have placed my code pr_name.java file in (/Code/Java/) Directory.
• I have Added the Description, Approach, and Working of Code at the beginning of Code.
• I have added 2 or more Testcases at the Bottom side of the Code.
• I have Added Time and Space Complexity at the End of the Code.
• I have Explained the Variables use in Complexity e.g. O(n) where n is the length of an array.
• I have Updated the Readme Related to the Topics e.g., if the issue is regarding Matrix then Update the Readme.MD present in 2D_Array Folder.
• I have added Proper Comments in between the Code for Better Explanation.
• I have sorted the list of the Readme.MD where I have added the issue in the Alphabetical Order.

[github-actions]

AlgoTree team will review your PR soon. Take Care of Few of the Things where most contributors are missing out. @yashigupta4623 :)