PLG: encode URL search params (#63275)

Fixes bug intorduced in
https://github.com/sourcegraph/sourcegraph/pull/63231

Encode the URL search params added to `returnTo` search param value.

Previously the search param value hasn't been encoded resulting in URLs
with broken search params , e.g.
*"/sign-in?returnTo=/cody/manage?teamID=1&inviteID=2"* (note the second
"?" making the search params invalid).



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## Test plan
- CI
- Tested manually:
- Make `signOutAndRedirectToSignIn` available in the window object, e.g.
`window.signOutAndRedirectToSignIn = signOutAndRedirectToSignIn` in the
*client/web/src/cody/management/api/react-query/callCodyProApi.ts*
- On "/cody/manage" page (any page works actually) ensure that a few
search params are added to the URL
   - call `signOutAndRedirectToSignIn` in the browser console
- ensure you have been sign out, signed back in and the search params
are still in the URL
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## Changelog

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source|search|ci|release|plg|cody|local|...
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Author: taras-yemets

client/web/src/cody/management/api/react-query/callCodyProApi.ts

@@ -31,7 +31,9 @@ const buildRequestInit = ({ headers = {}, ...init }: RequestInit): RequestInit =
 const signOutAndRedirectToSignIn = async (): Promise<void> => {
     const response = await fetch('/-/sign-out', buildRequestInit({ method: 'GET' }))
     if (response.ok) {
-        window.location.href = `/sign-in?returnTo=${window.location.pathname + window.location.search}`
+        window.location.href = `/sign-in?returnTo=${
+            window.location.pathname + encodeURIComponent(window.location.search)
+        }`
     }
 }