match cases for labels on search page

**Describe the issue / enhancement**
s/"Hide historic/obsoleted"/"Hide Historic/Obsoleted" for check box on the search page to match case of labels above

**Link(s) to relevant page(s)**
(https://www.rfc-editor.org/search)

<img width="1270" height="259" alt="Image" src="https://github.com/user-attachments/assets/d1a45f03-0b61-4bc4-93b5-117fead48e08" />