Remove broken image walkthrough from metamaskbot comment

[whymarrh]

This PR remove the "walkthrough" from the metamaskbot comment on PRs here on GH.

For reference: on the more recent comments from metamaskbot is #6358 (comment)

[kumavis]

related #6371

[metamaskbot]

Builds ready [a765df6]:
<a href="https://86514-42009758-gh.circle-artifacts.com/0/builds/metamask-chrome-6.3.0.zip">chrome</a>,
<a href="https://86514-42009758-gh.circle-artifacts.com/0/builds/metamask-firefox-6.3.0.zip">firefox</a>,
<a href="https://86514-42009758-gh.circle-artifacts.com/0/builds/metamask-edge-6.3.0.zip">edge</a>,
<a href="https://86514-42009758-gh.circle-artifacts.com/0/builds/metamask-opera-6.3.0.zip">opera</a>

[kumavis]

@whymarrh well that did not come out how i expected it... i think because it has consistent whitespace on the left

[metamaskbot]

Builds ready [0762aaa]: chrome, firefox, edge, opera