perf: remove breakpoint value of col argument

Author: thingsym

docs/index.html

@@ -521,8 +521,8 @@ <h3 class="reference"><span class="small">@include</span> <span class="big">grid
     <tr>
     <td>$col</td>
     <td>null</td>
-    <td>null | initial | &lt;<a href="http://www.w3.org/TR/CSS21/syndata.html#numbers" target="_blank">number</a>&gt; | auto | equal | none | breakpoint | positive | &lt;<a href="http://www.w3.org/TR/CSS21/visudet.html#the-width-property" target="_blank">width</a>&gt;</td>
-    <td>define columns. <code>null</code> is no set columns. <code>&lt;number&gt;</code> is number of columns. <code>initial</code>, <code>auto</code>, <code>equal</code>, <code>none</code>, <code>breakpoint</code> and <code>positive</code> are preset columns. <code>&lt;width&gt;</code> is unit set columns (<code>&lt;width&gt;</code> is experimental stage. <code>&lt;breakpoint&gt;</code> is deprecated, use <code>&lt;initial&gt;</code> instead).</td>
+    <td>null | initial | &lt;<a href="http://www.w3.org/TR/CSS21/syndata.html#numbers" target="_blank">number</a>&gt; | auto | equal | none | positive | &lt;<a href="http://www.w3.org/TR/CSS21/visudet.html#the-width-property" target="_blank">width</a>&gt;</td>
+    <td>define columns. <code>null</code> is no set columns. <code>&lt;number&gt;</code> is number of columns. <code>initial</code>, <code>auto</code>, <code>equal</code>, <code>none</code>, <code>positive</code> are preset columns. <code>&lt;width&gt;</code> is unit set columns (<code>&lt;width&gt;</code> is experimental stage. <code>&lt;breakpoint&gt;</code> is deprecated, use <code>&lt;initial&gt;</code> instead).</td>
     <td class="example"><a href="example/example.html#preset-grid-columns"><i class="fas fa-external-link-alt"></i></a></td>
     </tr>
     <tr>

sass/_flexbox-grid-mixins.scss

@@ -106,12 +106,6 @@ $flexbox-grid-mixins-box-sizing: border-box !default;
 		$flex-grow: 0;
 		$flex-shrink: 1;
 		$flex-basis: auto;
-	} @else if type-of($col) == string and $col == 'breakpoint' {
-		// deprecated
-		$flex-grow: 0;
-		$flex-shrink: 1;
-		$flex-basis: auto;
-		$width: 100%;
 	} @else if type-of($col) == string and $col == 'positive' {
 		// positive number
 		@if $flex-grow == 0 {