Deprecate IDBEnvironment mixin (#5600)
Deprecate IDBEnvironment mixin (#5600)

https://github.com/w3c/IndexedDB/commit/8c2196a and
https://github.com/w3c/IndexedDB/commit/44d82bf completely removed the
IDBEnvironment mixin from the Indexed DB spec. The indexedDB property it
had provided was moved to the WindowOrWorkerGlobalScope mixin.

https://github.com/w3c/IndexedDB/pull/95
mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data