Fix/consolidated reverse long words and reverse letters

[AnshuSharma111]

Describe your change:

Deleted reverse_long_words.py and modified code of reverse_letters.py to integrate functionality of reverse_long_words.py. Both had almost same function of reversing the letters of words in a sentence without reversing the words.

1. Deleted reverse_long_words.py
2. Implemented its functionality to reverse_letters.py because both had same function
3. Changed Directory.md to reflect changes

Fixes #8098

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
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• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
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[algorithms-keeper]

Closing this pull request as invalid

@AnshuSharma111, this pull request is being closed as none of the checkboxes have been marked. It is important that you go through the checklist and mark the ones relevant to this pull request. Please read the Contributing guidelines.

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