fixes #21511: set line-height to 1.1 for display headings

- had to rearrange vars to re-use heading line-height
- align values while we're at it

scss/_type.scss

@@ -27,18 +27,22 @@ h6, .h6 { font-size: $font-size-h6; }
 .display-1 {
   font-size: $display1-size;
   font-weight: $display1-weight;
+  line-height: $display-line-height;
 }
 .display-2 {
   font-size: $display2-size;
   font-weight: $display2-weight;
+  line-height: $display-line-height;
 }
 .display-3 {
   font-size: $display3-size;
   font-weight: $display3-weight;
+  line-height: $display-line-height;
 }
 .display-4 {
   font-size: $display4-size;
   font-weight: $display4-weight;
+  line-height: $display-line-height;
 }
 
 

scss/_variables.scss

@@ -270,22 +270,23 @@ $font-size-h4: 1.5rem !default;
 $font-size-h5: 1.25rem !default;
 $font-size-h6: 1rem !default;
 
-$display1-size: 6rem !default;
-$display2-size: 5.5rem !default;
-$display3-size: 4.5rem !default;
-$display4-size: 3.5rem !default;
-
-$display1-weight: 300 !default;
-$display2-weight: 300 !default;
-$display3-weight: 300 !default;
-$display4-weight: 300 !default;
-
 $headings-margin-bottom: ($spacer / 2) !default;
 $headings-font-family:   inherit !default;
 $headings-font-weight:   500 !default;
 $headings-line-height:   1.1 !default;
 $headings-color:         inherit !default;
 
+$display1-size: 6rem !default;
+$display2-size: 5.5rem !default;
+$display3-size: 4.5rem !default;
+$display4-size: 3.5rem !default;
+
+$display1-weight:     300 !default;
+$display2-weight:     300 !default;
+$display3-weight:     300 !default;
+$display4-weight:     300 !default;
+$display-line-height: $headings-line-height !default;
+
 $lead-font-size:   1.25rem !default;
 $lead-font-weight: 300 !default;