Add subtext to why Always show tabs is not toggleable in SUI. (#15154)

## Summary of the Pull Request
Add subtext that lets the user know why Always show tabs is not
toggleable in SUI. Also adds some additional information to the comment
for this value that points to the Globals_ShowTitlebar.Header setting.

## References and Relevant Issues
#13984 
## Detailed Description of the Pull Request / Additional comments
Simple updates to the resources that add some additional helpful
information for the user.
## Validation Steps Performed
Verified the updates show in the SUI and that they render correctly.
## PR Checklist
- [ ] Closes #13984 
- [ ] Tests added/passed
- [ ] Documentation updated
- If checked, please file a pull request on [our docs
repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
- [ ] Schema updated (if necessary)

---------

Co-authored-by: Mike Griese <migrie@microsoft.com>

src/cascadia/TerminalSettingsEditor/Resources/en-US/Resources.resw

@@ -244,8 +244,8 @@
     <comment>Header for a control to toggle if the app should always show the tabs (similar to a website browser).</comment>
   </data>
   <data name="Globals_AlwaysShowTabs.HelpText" xml:space="preserve">
-    <value>When disabled, the tab bar will appear when a new tab is created.</value>
-    <comment>A description for what the "always show tabs" setting does. Presented near "Globals_AlwaysShowTabs.Header".</comment>
+    <value>When disabled, the tab bar will appear when a new tab is created. Cannot be disabled while "Hide the title bar" is On.</value>
+    <comment>A description for what the "always show tabs" setting does. Presented near "Globals_AlwaysShowTabs.Header". This setting cannot be disabled while "Globals_ShowTitlebar.Header" is enabled.</comment>
   </data>
   <data name="Globals_NewTabPosition.Header" xml:space="preserve">
     <value>Position of newly created tabs</value>