remove blackfriday (#11161)

config.toml

@@ -17,23 +17,6 @@ staticDir = ["static", "generated"]
 disableAliases = true
 
 [markup]
-  defaultMarkdownHandler = "blackfriday"
-  [markup.blackfriday]
-    angledQuotes = false
-    footnoteAnchorPrefix = ""
-    footnoteReturnLinkContents = ""
-    fractions = true
-    hrefTargetBlank = false
-    latexDashes = true
-    nofollowLinks = false
-    noreferrerLinks = false
-    plainIDAnchors = true
-    skipHTML = false
-    smartDashes = true
-    smartypants = true
-    smartypantsQuotesNBSP = false
-    taskLists = true
-    extensions = [""]
   [markup.goldmark]
     [markup.goldmark.extensions]
       definitionList = true