Bug 1430512: Remove unnecessary use of -moz-border-bottom-colors in aboutBase.css. r=dao

A single color in the color list renders just as border-bottom-color.

This used to have two colors, but was changed in [1], so now it can go away.

[1]: https://hg.mozilla.org/mozilla-central/rev/cfdf310748918c3d5eadc16daa5153091e325995

MozReview-Commit-ID: LDocmCwjkzw

--HG--
extra : rebase_source : 0b5027434d7a964165f547c3c67f31045ecc3df4

mobile/android/themes/core/aboutBase.css

@@ -27,8 +27,7 @@ input {
   font-size: 1.1em;
   font-weight: bold;
   background-color: #f5f5f5;
-  border-bottom: 2px solid;
-  -moz-border-bottom-colors: #0A84FF;
+  border-bottom: 2px solid #0A84FF;
   display: flex;
   flex-direction: row;
   align-items: center;