Convert dependency check annotation from h3 to p

[mokagio]

An h3 (### markdown) in the CI annotation results in a message that clashes visually with the rest of the annotations.

See for example https://buildkite.com/automattic/simplenote-ios/builds/1146

Before

After via editing the HTML source in the page. No build run with this yet.

Test

We'll see this in action on the next code freeze.

Review

Only one infrastructure developer required to review these changes, but anyone can perform the review.

Release

These changes do not require release notes.

[mokagio]

I did this tidy because I thought I'd add an emoji an wanted to DRY the check.

I decided not to add the emoji to the text because Buildkite already has icons and colors for each annotation style. But I kept the code like this because I think it's a tiny readability improvements.

Also, since I'm on my way to write more commentary than code, I considered being explicit in the variable names and the message in mentioning CocoaPods. But, I'd say leaving it as generic "dependencies" makes it easier for us to update the logic to incorporate something that parses the Package.resolved JSON looking for dependencies that point to non stable versions.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Simplenote Prototype Build by scanning the QR code below to install the corresponding build.

	App Name	Simplenote Prototype Build
	Build Number	pr1663-bdc664e-0192082e-dc25-47d5-a033-6519cb0a760e
	Version	4.54
	Bundle ID	com.codality.NotationalFlow.Alpha
	Commit	bdc664e
	App Center Build	Simplenote - Installable Builds #385

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[AliSoftware]

WFM, but you'll have to update the wording of the task referencing that annotation in the ReleaseV2 scenario to match, now that the annotation has a different "title":