Rename unregisterTimeHistogram to unregisterDurationHistogram

[simonjbeaumont]

Motivation

The new 2.0 alpha APIs have asymmetric names for registering and unregistering duration histograms:

• makeValueHistogram 🙂
• unregisterValueHistogram 🙂
• makeDurationHistogram 🙂
• unregisterTimeHistogram 🧐

Modifications

• Rename unregisterTimeHistogram to unregisterDurationHistogram.

Result

APIs more symmetrically named.

⚠️ API breakage

This is an API breaking change and I have not provided a backwards compatible shim and deprecation notice, because we are currently at 2.0.0-alpha.1 and SemVer permits API breaks at this stage.

However, I'm happy to update the patch to include the temporary shim, if we want to add it now, and remove before 2.0.0 release.

[fabianfett]

@swift-server-bot test this please