delete IFSummary* and InterfaceStatus macros

[wbamberg]

This PR deletes 4 interrelated macros that are no longer used now that we've cleaned macros from the XPCOM docs.

IFSummaryEnd

• References across MDN content: https://developer.mozilla.org/en-US/search?locale=*&kumascript_macros=IFSummaryEnd&topic=none
• References across KS codebase: https://github.com/mdn/kumascript/search?q=IFSummaryEnd&unscoped_q=IFSummaryEnd

(called from IFSummary, but we're also removing that in this PR)

IFSummaryStart

• References across MDN content: https://developer.mozilla.org/en-US/search?locale=*&kumascript_macros=IFSummaryStart&topic=none
• References across KS codebase: https://github.com/mdn/kumascript/search?q=IFSummaryStart&unscoped_q=IFSummaryStart

(called from IFSummary, but we're also removing that in this PR)

InterfaceStatus

• References across MDN content: https://developer.mozilla.org/en-US/search?locale=*&kumascript_macros=InterfaceStatus&topic=none
• References across KS codebase: https://github.com/mdn/kumascript/search?q=InterfaceStatus&unscoped_q=InterfaceStatus

IFSummary

• References across MDN content: https://developer.mozilla.org/en-US/search?locale=*&kumascript_macros=IFSummary&topic=none
• References across KS codebase: https://github.com/mdn/kumascript/search?q=IFSummary&unscoped_q=IFSummary

(called from InterfaceStatus, but we're also removing that in this PR)

[wbamberg]

Added a commit to delete VersionTimeline, which is only called by IFSummaryEnd:

• References across MDN content: https://developer.mozilla.org/en-US/search?locale=*&kumascript_macros=VersionTimeline&topic=none
• References across KS codebase: https://github.com/mdn/kumascript/search?q=VersionTimeline&unscoped_q=VersionTimeline

[wbamberg]

Added a commit to delete the delightfully named xverblob, which is only called by VersionTimeline:

• References across MDN content: https://developer.mozilla.org/en-US/search?locale=*&kumascript_macros=xverblob&topic=none
• References across KS codebase: https://github.com/mdn/kumascript/search?q=xverblob&unscoped_q=xverblob

[escattone]

☠️ 🎉 Awesome @wbamberg!