chore(global): remove unused context references (#27634)

Issue number: N/A

---------

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## What is the current behavior?
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Ionic Framework references a deprecated object,`Context`, exposed by
Stencil

## What is the new behavior?
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this PR. -->

starting with stencil v4, the deprecated `Context` object will no longer
be exposed by stencil. this change was introduced in
https://github.com/ionic-team/stencil/pull/4437, and will be present in
the first v4 prerelease following v4.0.0-beta.2. in anticipation for
this change, we seek to remove references to `Context` early.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No - To the best of my knowledge

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and migration path for existing applications below. -->


## Other information

ATM, the Stencil v4 nightly build is passing, as it's grabbing
`@stencil/core@4.0.0-beta.2`. The change in which we remove the
`Context` object will occur in the _next_ pre-release. I'm removing
`Context` here to try to get a jump on things.


The current iteration of the code that I'm deleting was added in
c415bbe1d7 (diff-ce62e75f0c31a76aac491f13a64e9c7771a6cbae8ca6635541164b69f0479bf1)
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screenshots of how the component looks before and after the change. -->

core/src/global/ionic-global.ts

@@ -7,8 +7,6 @@ import { config, configFromSession, configFromURL, saveConfig } from './config';
 
 // TODO(FW-2832): types
 
-declare const Context: any;
-
 let defaultMode: Mode;
 
 export const getIonMode = (ref?: any): Mode => {
@@ -22,7 +20,6 @@ export const initialize = (userConfig: IonicConfig = {}) => {
 
   const doc = window.document;
   const win = window;
-  Context.config = config;
   const Ionic = ((win as any).Ionic = (win as any).Ionic || {});
 
   const platformHelpers: any = {};