Fix typos in user-facing localized strings

[kbhujbal]

• Fix "Overriden" -> "Overridden" in terminal cwd picker description
• Fix "requried" -> "required" in notebook renderer messaging description

[kbhujbal]

Fixes typos in two user-facing localized strings:

• terminalActions.ts: "(Overriden) {0}" → "(Overridden) {0}" — visible in the terminal cwd picker when a folder's working directory is overridden.
• notebookExtensionPoint.ts: "it's not requried." → "it's not required." — visible in the notebook renderer requiresMessaging enum description.

Both are simple spelling corrections in nls.localize() message strings with no functional changes.

Test plan

• Verify the two changed strings render correctly in the UI
• No functional code was modified — only localized string literals

[kbhujbal]

@microsoft-github-policy-service agree