[chore] Update exercise discussion and pull request templates (#227)

# Exercise Review

## Exercise Discussion

N/A

## Checklist

- [ ] If you require a new remote repository on the `Git-Mastery`
organization, have you [created a
request](https://github.com/git-mastery/exercises/issues/new?template=request_exercise_repository.md)
for it?
- [ ] Have you written unit tests using
[`repo-smith`](https://github.com/git-mastery/repo-smith) to validate
the exercise grading scheme?
- [ ] Have you tested your changes using the instructions posted?
- [ ] Have you verified that this exercise does not already exist or is
not currently in review?
- [ ] Did you introduce a new grading mechanism that should belong to
[`git-autograder`](https://github.com/git-mastery/git-autograder)?
- [ ] Did you introduce a new dependency that should belong to
[`app`](https://github.com/git-mastery/app)?

Author: VikramGoyal23

.github/ISSUE_TEMPLATE/exercise_discussion.yaml

@@ -17,7 +17,7 @@ body:
     attributes:
       label: Existing exercise check
       options:
-        - label: I have verified that this exercise is not yet already [in discussion](https://github.com/git-mastery/exercises/issues?q=is%3Aissue%20state%3Aopen%20label%3A%22exercise%20discussion%22), [in progress](https://github.com/git-mastery/exercises/pulls?q=is%3Aopen+is%3Apr+label%3A%22exercise+review%22), or [exists](https://git-mastery.github.io/exercise)
+        - label: I have verified that this exercise is not yet already [in discussion](https://github.com/git-mastery/exercises/issues?q=is%3Aissue%20state%3Aopen%20label%3A%22exercise%20discussion%22), [in progress](https://github.com/git-mastery/exercises/pulls?q=is%3Aopen+is%3Apr+label%3A%22exercise+review%22), or [exists](https://git-mastery.org/exercises-directory/index.html)
           required: true
   - type: input
     attributes:

.github/pull_request_template.md

@@ -6,7 +6,7 @@ Link the exercise discussion issue
 
 ## Checklist
 
-- [ ] If you require a new remote repository on the `Git-Mastery` organization, have you [created a request](https://github.com/git-mastery/exercises/issues/new?template=request_exercise_repository.md) for it?
+- [ ] If you require a new remote repository on the `Git-Mastery` organization, have you [created a request](https://github.com/git-mastery/exercises/issues/new?template=request_exercise_repository.yaml) for it?
 - [ ] Have you written unit tests using [`repo-smith`](https://github.com/git-mastery/repo-smith) to validate the exercise grading scheme?
 - [ ] Have you tested your changes using the instructions posted?
 - [ ] Have you verified that this exercise does not already exist or is not currently in review?