docs: remove Gitter from issue templates

[ersachin3112]

This PR contains a:

• [ ] bugfix
• [ ] new feature
• [ ] code refactor
• [ ] test update
• [ ] typo fix
• [x] metadata update

Motivation / Use-Case

remove Gitter from issue templates

Breaking Changes

No

Additional Info

No

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (c05a156) 82.26% compared to head (3e36599) 82.26%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #215 +/- ## ======================================= Coverage 82.26% 82.26% ======================================= Files 4 4 Lines 141 141 Branches 51 51 ======================================= Hits 116 116 Misses 16 16 Partials 9 9 ```

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