Update thumbsup and thumbsdown icons

[colebemis]

The current thumbsup and thumbsdown octicons have always felt a little too cartoony to me and don't match the style of the rest of the icons. I took a stab at redesigning them:

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: e2a199c6bba0ee1aa80bc23146ad6744f69fecc4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ---------------- | ----- | | @primer/octicons | Minor |

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[samoshin]

I'm inclined to 👍 it 😏 . @tallys?

[tallys]

LGTM 👍 👍

[tallys]

cc @lukasoppermann

[lukasoppermann]

LGTM