Include setting Firefox (default) search engine./Update policies.json

## Search Engines
The (apt) Firefox search engines were initially set using a `policies.json` file. HOwever that is not supported for non-ESR firefox.
See: https://access.redhat.com/solutions/6707711
And:
https://support.mozilla.org/en-US/questions/1295935
suggests it may be done using the
autoconfig.cfg

## Update policies.json
Some elements in the current `policies.json` file are outdated:
```
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console.warn: services.settings: Ignoring preference override of remote settings server
console.warn: services.settings: Allow by setting MOZ_REMOTE_SETTINGS_DEVTOOLS=1 in the environment
console.error: Policies.jsm:
'ExpireAtSessionEnd' has been deprecated and it has no effect anymore.
console.error: ({})
console.error: (new TypeError("NetworkError: Network request failed", "resource://services-settings/Utils.jsm", 237))
console.error: Policies.jsm:
Download failed - ERROR_NETWORK_FAILURE - https://addons.mozilla.org/firefox/downloads/latest/bypass-paywalls-clean/latest.xpi
console.error: Policies.jsm:
Download failed - ERROR_NETWORK_FAILURE - https://addons.mozilla.org/firefox/downloads/latest/https-everywhere/latest.xpi
*** You are running in background task mode. ***
*** You are running in headless mode.
console.error: Policies.jsm:
'ExpireAtSessionEnd' has been deprecated and it has no effect anymore.
console.error: "/home/name/.mozilla/firefox/kwz4y9x4.default-release/storage" "to-be-removed" 0 "" ""
JavaScript error: resource://gre/modules/AddonManager.jsm, line 3030: NS_ERROR_NOT_INITIALIZED: AddonManager is not initialized
[ERROR glean_core] Error setting metrics feature config: Json(Error("EOF while parsing a value", line: 1, column: 0))
console.error: "Cache folder attempt no 1"
console.error: "couldn't find cache folder /home/name/.mozilla/firefox/kwz4y9x4.default-release/storage/to-be-removed"
console.warn: "Skipping Glean as no metrics id is passed"
JavaScript error: undefined, line 0: Error: Content script already unregistered
JavaScript error: undefined, line 0: Error: Content script already unregistered
JavaScript error: undefined, line 0: Error: Content script already unregistered
JavaScript error: undefined, line 0: Error: Content script already unregistered
Extension error: TypeError: sender.tab is undefined moz-extension://520d087f-9a99-4fa7-9d0d-0038c91373ab/background_scripts/main.js 438
[[Exception stack
onConnect@moz-extension://520d087f-9a99-4fa7-9d0d-0038c91373ab/background_scripts/main.js:438:31
@moz-extension://520d087f-9a99-4fa7-9d0d-0038c91373ab/background_scripts/main.js:87:62
Current stack
applySafeWithoutClone@resource://gre/modules/ExtensionCommon.jsm:707:41
addListener/asyncWithoutClone/<@resource://gre/modules/ExtensionCommon.jsm:2644:39
]]
JavaScript error: moz-extension://92f75756-5a29-4de8-a1ce-457beb62c983/dist/content_script_bundle.js, line 122: TypeError: u.app is undefined
Extension error: TypeError: can't convert undefined to object moz-extension://f7be818a-fb93-4878-89b8-fa1bbd66ebf8/content.js 50
[[Exception stack
Go/