[semver:patch] Replace the name diagnostic-orb with build-tools

[lukyth]

Checklist

• [ ] All new jobs, commands, executors, parameters have descriptions
• [ ] Examples have been added for any significant new features
• [ ] README has been updated, if necessary

Motivation, issues

I was trying to use this orb but the example on the website (https://circleci.com/orbs/registry/orb/circleci/build-tools#usage-debug-ios-job) and in this repo (https://github.com/CircleCI-Public/build-tools-orb/tree/master/src/examples) is using the wrong orb name. From https://github.com/CircleCI-Public/build-tools-orb/issues/6, I'd assume this is the remaining of the old name. That's why I want to get rid of them so no one else would get confused like me.

Description

• Replaced diagnostic-orb with build-tools
• Replace the orb version in the example from 1.0.0 to the current version, 2.6.3.

[gmemstr]

@lukyth Thank you for the contribution! Would you mind changing the recent version to x.y.z for the time being? We're working on a better method of versioning examples.

[lukyth]

@gmemstr No problem! 😄 I've updated the version to x.y.z with f1382b2 now.