feat: upgrade Classic font pack to GFonts API v2 (#2516)

Small update to fix error re: Google fonts on Classic font set. Without this change Hugo raises the following ERROR:

"There is a new version of Google Fonts. Learn how to upgrade your font pack at https://wowchemy.com/docs/customization/#custom-font
Error: Error building site: logged 1 error(s)"

wowchemy/data/fonts/classic.toml

@@ -2,7 +2,7 @@
 name = "Classic"
 
 # Optional Google font URL
-google_fonts = "Lato:400,700|Merriweather|Roboto+Mono"
+google_fonts = "family=Lato:wght@400;700&family=Merriweather&family=Roboto+Mono"
 
 # Font families
 heading_font = "Lato"