Chore: fixed punctuation errors

[Cyebukayire]

What kind of change does this PR introduce? (check at least one)

• [ ] Bugfix
• [ ] Feature
• [ ] Code style update
• [ ] Refactor
• [ ] Build-related changes
• [x] Other, please describe:

PR DESCRIPTION:

1. v-model, transition etc... A comma precedes the use of “etc.,” whether abbreviated or written as “et cetera,” because it's another item on the list.

2. ** feat, fix or perf** In the same case as above, "perf" is also considered as another item on the list.

SUGGESTED SOLUTION

1. v-model, transition, etc...
2. feat, fix, or perf

Does this PR introduce a breaking change? (check one)

• [ ] Yes
• [x] No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• [x] It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• [x] When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• [x] All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• [x] New/updated tests are included

If adding a new feature, the PR's description includes:

• [x] A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information: