Fixed round buttons' icon centering

Fixes #3576

bigbluebutton-html5/imports/ui/components/button/styles.scss

@@ -43,7 +43,7 @@ $btn-jumbo-padding: $jumbo-padding-y $jumbo-padding-x;
   display: inline-block;
   border-radius: $border-size;
   font-weight: $btn-font-weight;
-  line-height: 1.5;
+  line-height: 1;
   text-align: center;
   white-space: nowrap;
   vertical-align: middle;

bigbluebutton-html5/imports/ui/stylesheets/variables/general.scss

@@ -4,13 +4,13 @@ $border-size-large: 3px;
 $border-radius: .2rem;
 
 $sm-padding-x: .75rem;
-$sm-padding-y: .25rem;
+$sm-padding-y: .3rem;
 
 $md-padding-x: 1rem;
-$md-padding-y: .375rem;
+$md-padding-y: .45rem;
 
 $lg-padding-x: 1.25rem;
-$lg-padding-y: .5rem;
+$lg-padding-y: 0.6rem;
 
 $jumbo-padding-x: 3.025rem;
-$jumbo-padding-y: 1.25rem;
+$jumbo-padding-y: 1.5rem;