doc: add missing colon to headers in globals.md

PR-URL: #58825
Reviewed-By: Ryuhei Shima <shimaryuhei@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>

Author: avivkeller

doc/api/globals.md

@@ -621,7 +621,7 @@ added: v20.0.0
 
 See {File}.
 
-## Class `FormData`
+## Class: `FormData`
 
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 added:
@@ -660,7 +660,7 @@ the global scope; `var something` inside a Node.js module will be local to that
 module, regardless of whether it is a [CommonJS module][] or an
 [ECMAScript module][].
 
-## Class `Headers`
+## Class: `Headers`
 
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 added: