bootstrap: Remove body selectors, zero margin/padding explicitly.

web/styles/zulip.css

@@ -21,6 +21,8 @@ html {
 
 body {
     width: 100%;
+    margin: 0;
+    padding: 0;
     font-size: 14px;
     line-height: calc(20 / 14);
     font-family: "Source Sans 3 VF", sans-serif;
@@ -3198,10 +3200,6 @@ select.invite-as {
 }
 
 @media (width < $md_min) {
-    body {
-        padding: 0;
-    }
-
     .column-left {
         display: none;
 

web/third/bootstrap/css/bootstrap.app.css

@@ -57,10 +57,6 @@ label,
 button {
   cursor: pointer;
 }
-body {
-  margin: 0;
-  line-height: 20px;
-}
 a {
   color: #0088cc;
   text-decoration: none;
@@ -312,12 +308,6 @@ button.close {
   display: none;
   visibility: hidden;
 }
-@media (max-width: 767px) {
-  body {
-    padding-left: 20px;
-    padding-right: 20px;
-  }
-}
 @media (min-width: 768px) and (max-width: 979px) {
   input {
     margin-left: 0;
@@ -328,8 +318,3 @@ button.close {
     margin-left: 0;
   }
 }
-@media (max-width: 979px) {
-  body {
-    padding-top: 0;
-  }
-}