minor fix in first exemple (#4066)

Tarrask · jacobmllr95 · commit 7e5621bc1fad · 2019-09-10T12:46:33.000+02:00
Closing tag in the first exemple is 'b-popover' instead of 'b-tooltip'
diff --git a/src/components/tooltip/README.md b/src/components/tooltip/README.md
@@ -14,7 +14,7 @@
   </b-button>
   <b-tooltip target="tooltip-target-1" triggers="hover">
     I am tooltip <b>component</b> content!
-  </b-popover>
+  </b-tooltip>
 </div>
 
 <!-- b-tooltip.vue -->
