Remove unnecessary CSS property from header (#4227)

This CSS rule was causing conversation header text to be truncated even
when there was enough whitespace to display the entire text at certain
zoom levels and platforms.

Removing the property did not introduce any UI regressions from this
author's testing.

Fixes: #3168

stylesheets/_modules.scss

@@ -2664,8 +2664,6 @@ $timer-icons: '55', '50', '45', '40', '35', '30', '25', '20', '15', '10', '05',
 
   @include font-body-1-bold;
 
-  // width of avatar (28px) and our 6px left margin
-  max-width: calc(100% - 34px);
   white-space: nowrap;
   overflow: hidden;
   text-overflow: ellipsis;