Add missing "Protocol" to the title

stzn · web-flow · commit da2ca7a4d403 · 2024-04-25T04:44:19.000+09:00
In the content, "boxed protocol types" is used, but it's not used in the title.
diff --git a/TSPL.docc/LanguageGuide/OpaqueTypes.md b/TSPL.docc/LanguageGuide/OpaqueTypes.md
@@ -1,4 +1,4 @@
-# Opaque and Boxed Types
+# Opaque and Boxed Protocol Types
 
 Hide implementation details about a value's type.
 

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-# Opaque and Boxed Types`
	`1`	`+# Opaque and Boxed Protocol Types`
`2`	`2`
`3`	`3`	`Hide implementation details about a value's type.`
`4`	`4`