LG-6485: Update line height value for accordion component (#316)

* LGDS: Update line height value for accordion component

**Why**: To improve readability when the accordion heading spans multiple lines of text.

* Sync banner accordion button to text

Decrease from 1.5 to 1.2 to match

See: #316 (comment)

CHANGELOG.md

@@ -1,3 +1,9 @@
+## Unreleased
+
+### Improvements
+
+- Increase line-height for accordion heading content to improve readability. ([#316](https://github.com/18F/identity-style-guide/pull/316))
+
 ## 6.4.2
 
 ### Dependencies

src/scss/components/_accordions.scss

@@ -6,6 +6,7 @@
   background-color: color('transparent');
   background-size: units(2);
   color: color('primary');
+  line-height: line-height($theme-body-font-family, $theme-body-line-height);
 
   &:hover {
     background-color: color('primary-lightest');

src/scss/components/_banner.scss

@@ -19,6 +19,7 @@
   // Reset default accordion button border styling for banner button.
   @include u-border(0);
   @include u-radius(0);
+  line-height: line-height($theme-banner-font-family, 2);
 }
 
 .usa-accordion__button.usa-banner__button,