Align font-weight of heading-classes with elements

Currently the heading-level css classes (.h1 - .h6) have a different
font-weight than their related heading elements.

This commit aligns the the font-weight and uses $gl-font-weight-bold
to set it.

app/assets/stylesheets/bootstrap_migration.scss

@@ -41,16 +41,6 @@ html [type="button"],
   cursor: pointer;
 }
 
-h1,
-h2,
-h3,
-h4,
-h5,
-h6 {
-  color: $gl-text-color;
-  font-weight: 600;
-}
-
 h1,
 .h1,
 h2,

app/assets/stylesheets/framework/typography.scss

@@ -567,16 +567,6 @@ body {
   font-weight: $gl-font-weight-bold;
 }
 
-h1,
-h2,
-h3,
-h4,
-h5,
-h6 {
-  color: $gl-text-color;
-  font-weight: $gl-font-weight-bold;
-}
-
 .light-header {
   font-weight: $gl-font-weight-bold;
 }

app/assets/stylesheets/framework/variables_overrides.scss

@@ -35,6 +35,8 @@ $h3-font-size: 14px * 1.75;
 $h4-font-size: 14px * 1.5;
 $h5-font-size: 14px * 1.25;
 $h6-font-size: 14px;
+$headings-color: $gl-text-color;
+$headings-font-weight: $gl-font-weight-bold;
 $spacer: $grid-size;
 $spacers: (
   0: 0,

changelogs/unreleased/dpisek-use-right-font-weight-for-hN-classes.yml

+---
+title: Align color and font-weight styles of heading elements and their typography
+  classes
+merge_request: 28422
+author:
+type: other