Fix screenshot URLs in contents.json (#2023)

Updated screenshot URLs to use lowercase file names.

Author: csprasad

contents.json

@@ -32927,8 +32927,8 @@
         "swift"
       ],
       "screenshots": [
-        "https://github.com/csprasad/Mr-Tip/raw/main/Mr.%20Tip/screenshots/Light.png",
-        "https://github.com/csprasad/Mr-Tip/raw/main/Mr.%20Tip/screenshots/Dark.png"
+        "https://github.com/csprasad/Mr-Tip/raw/main/Mr.%20Tip/screenshots/light.png",
+        "https://github.com/csprasad/Mr-Tip/raw/main/Mr.%20Tip/screenshots/dark.png"
       ],
       "date_added": "Apr 14 2025",
       "suggested_by": "@csprasad",