fix a few editorial bugs

sections/semantics-embedded-content.include

@@ -901,7 +901,7 @@
 
   The <dfn element-attr for="img"><code>decoding</code></dfn> attribute is an enumerated attribute.
   It is an [=image decoding hint=] to request synchronous or asynchronous image loading.
-  Valid values are "<code>async</code>", "<code>async</code>", and "<code>auto</code>".
+  Valid values are "<code>sync</code>", "<code>async</code>", and "<code>auto</code>".
   The [=missing value default=] and [=invalid value default=] are both "<code>auto</code>".
 
   The <dfn element-attr for="img"><code>referrerpolicy</code></dfn> attribute is a <a>referrer policy attribute</a>.

sections/syntax.include

@@ -5066,7 +5066,7 @@
 
         [=Insert an HTML element=] for the token.
 
-    : A start tag whose tag name is one of: "rb", "rtc"
+    : A start tag whose tag name is: "rb"
     :: If the [=stack of open elements=] <a lt="in scope">has a `ruby` element in scope</a>, then
         [=generate implied end tags=]. If the [=current node=] is not now a <{ruby}> element nor 
         a child of a <{ruby}> element, this is a [=parse error=].
@@ -5080,6 +5080,12 @@
 
         [=Insert an HTML element=] for the token.
 
+    : A start tag whose tag name is: "rtc"
+    :: If the [=stack of open elements=] <a lt="in scope">has a `ruby` element in scope</a>, then
+        [=generate implied end tags=]. If the [=current node=] is not now a <{ruby}> element, this is a [=parse error=].
+
+        [=Insert an HTML element=] for the token.
+
     : A start tag whose tag name is "math"
     :: [=Reconstruct the active formatting elements=], if any.