rustdoc: remove no-op .method { font-size: 1rem }

This rule was added in 22dad4b044, back when
the `method` class was attached to headers instead of DIVs that wrap
headers.

Old method rendering:

a96247bcac/src/librustdoc/html/render.rs (L2062)

Current method rendering:

432abd86f2/src/librustdoc/html/render/print_item.rs (L721)

src/librustdoc/html/static/css/rustdoc.css

@@ -729,7 +729,6 @@ pre, .rustdoc.source .example-wrap {
 }
 
 .content > .methods > .method {
-	font-size: 1rem;
 	position: relative;
 }
 /* Shift "where ..." part of method or fn definition down a line */