Remove legacy chat closure notices

[jsnajdr]

Removes two unused components that used to display a "chat closed" notices.

The first one is HelpContactClosed that is simply not imported anywhere. There is another component, LiveChatClosureNotice, that does the same job and is actively used.

The second one is ChatBusinessConciergeNotice which was used for an one-off experiment back in 2017 and the code was never removed. See #16144.

@hewsut inspired me to take a closer look when I was looking at his #32276 🙂

[matticbot]

Test live: https://calypso.live/?branch=remove/legacy-closure-notices

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

App Entrypoints
Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

name            parsed_size    gzip_size
domainsLanding         +0 B         +8 B  (+0.0%)
build                  +0 B         +8 B  (+0.0%)

Sections
Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

name  parsed_size           gzip_size
help      -1769 B  (-0.2%)     -479 B  (-0.5%)

Async-loaded Components
React components that are loaded lazily, when a certain part of UI is displayed for the first time.

name                                   parsed_size           gzip_size
async-load-blocks-inline-help-popover      -2318 B  (-0.4%)     -566 B  (-1.3%)

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[mhsdef]

The best kind of PR, lovely. LGTM.