remove default left-right print margins per upstream h5bp change

Refs:
    https://github.com/h5bp/html5-boilerplate/commit/57be193031b95b003b96efe9eba7a4db7f58f4e1
    https://github.com/h5bp/html5-boilerplate/issues/1477

dist/css/bootstrap.css

@@ -213,9 +213,6 @@ table {
   img {
     max-width: 100% !important;
   }
-  @page {
-    margin: 2cm .5cm;
-  }
   p,
   h2,
   h3 {
@@ -232,6 +229,10 @@ table {
   .navbar {
     display: none;
   }
+  @page {
+    margin-top: 2cm;
+    margin-bottom: 2cm;
+  }
   .table td,
   .table th {
     background-color: #fff !important;

less/print.less

@@ -50,10 +50,6 @@
     max-width: 100% !important;
   }
 
-  @page {
-    margin: 2cm .5cm;
-  }
-
   p,
   h2,
   h3 {
@@ -76,6 +72,10 @@
   .navbar {
     display: none;
   }
+  @page {
+    margin-top:    2cm;
+    margin-bottom: 2cm;
+  }
   .table {
     td,
     th {