Update PULL_REQUEST_TEMPLATE.md

[aemino]

Please describe the changes this PR makes and why it should be merged:
Fixes weird spaces in the template and reorganizes options in ascending semver order: patch > minor > major

Semantic versioning classification:

• This PR changes the library's interface (methods or parameters added)
• This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
• This PR only includes non-code changes, like changes to documentation, README, etc.

[iCrawl]

I think the space was meant to be there, considering you check the first one, and if its breaking the second one. They are linked, since you cannot not change the interface without breaking it.

[meew0]

@iCrawl is right, the space is intended exactly as described. In PRs where it wasn't deleted (for example #1443) you can see how the checkmark is indented one level.