[css-mixins-1] Fix markup (#11686)

Co-authored-by: Tab Atkins Jr. <[email protected]>

Author: cdoublev

css-mixins-1/Overview.bs

@@ -179,7 +179,7 @@ The <dfn>@function</dfn> Rule {#function-rule}
 ----------------------------------------------
 
 The ''@function'' rule defines a <dfn>custom function</dfn>,
-and consists of a name (<<function-name>>),
+and consists of a name,
 a list of [=function parameter|parameters=],
 a <dfn for="custom function">function body</dfn>,
 and optionally a <dfn for="custom function">return type</dfn> described by a [=syntax definition=].
@@ -241,8 +241,11 @@ If more than one ''@function'' exists for a given name,
 then the rule in the stronger cascade layer wins,
 and rules defined later win within the same layer.
 
-If the <<function-parameter-list>>
-contains the same <<custom-property-name>> more than once,
+
+
+
+If the [=function parameters=]
+contain the same <<custom-property-name>> more than once,
 then the ''@function'' rule is invalid.
 
 <h4 id=function-body>
@@ -263,7 +266,7 @@ Additionally, it accepts the following descriptors:
 Unknown descriptors are invalid and ignored,
 but do not make the ''@function'' rule itself invalid.
 
-The '@function/result' Descriptor {#the-result-descriptor}
+The '@function/result' Descrip {#the-result-descriptor}
 ----------------------------------------------------------
 
 <pre class='descdef'>