Fix alias name of quoted_content in triple quoted strings

This was "quoted_contents" but should be "quoted_content" for
consistency with non-triple-quoted strings and sigils.

grammar.js

@@ -495,7 +495,7 @@ module.exports = grammar({
     _triple_quoted_string: ($) =>
       seq(
         field("quoted_start", '"""'),
-        optional(alias($._triple_quoted_string_contents, $.quoted_contents)),
+        optional(alias($._triple_quoted_string_contents, $.quoted_content)),
         field("quoted_end", '"""')
       ),
 

test/corpus/sigils.txt

@@ -62,4 +62,4 @@ All contents are verbatim, even this: ~r"abc\d+"i.
 (source
   (sigil
     (sigil_prefix)
-    (quoted_contents)))
+    (quoted_content)))

test/corpus/terms.txt

@@ -48,9 +48,9 @@ Hello "world"
 
 (source
   (string
-    (quoted_contents))
+    (quoted_content))
   (string
-    (quoted_contents)))
+    (quoted_content)))
 
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 atoms