Deleted one copy of linked list

[rucha174]

Fixes issue:
fixes issue #3934

Changes:
As per issue #3934 there were duplicate linked list. Removed this one in cosmos/code/data_structures/src/linked_list
kept the other one which is at cosmos/code/data_structures/src/list/singly_linked_list/singly_linked_list.c
Kept this one because the destination seems more relevant.

[arnavb]

@rucha174 I feel like the better option would be to replace the other file with the contents of this file, which is more thorough than what is already present.

[rucha174]

On it.

There was a confusion, which code is supposed to be kept and which one needs to be removed? Or do these entire directories need to be moved? (I am new to Open source, sorry for too much question)

[FR4NKESTI3N]

@rucha174 He means, replace respective files from list/singly_linked_list/ with files from linked_list/

@arnavb Should the preprocessor directives be removed from c and cpp code after replacement? Seems excessive.

[arnavb]

Right, I meant to say to remove this directory.

But before you do this, replace the implementations in this other directory with anything you feel is better from the deleted directory.

Also, yeah, the preprocessor directives aren't really necessary... not sure why they're there in a .cpp file. I assume the author probably meant to simulate a header file.

[rucha174]

I have created the pull request. Please review :)

[arnavb]

@rucha174 While opening a new PR is fine, do note that you can commit to the current one as well.