[css-flexbox-1] Drop styles with no matching ID (#5957)

Author: nschonni

css-flexbox-1/Overview.bs

@@ -63,11 +63,6 @@ spec: css-pseudo-4; type: selector;
 	text: ::first-letter
 </pre>
 
-<style>
-  #axis-mapping-table [rowspan=8] { writing-mode: sideways-lr; }
-  #axis-mapping-table a { white-space: nowrap; }
-</style>
-
 <style>
 code.one-line { white-space: pre;  }
 .code-and-figure {