Merge pull request #1113 from hypothesis/fix-annotation-body-headers

Fix overlapping text in headings in annotation bodies

src/styles/sidebar/styled-text.scss

 @mixin styled-text() {
+  // Reset the line-height in case any parent elements have set it.
+  line-height: normal;
+
   h1, h2, h3, h4, h5, h6, p, ol, ul, img, pre, blockquote {
     margin: .618em 0;
   }