This is an easy one. If you need to remove all of the tabs in your Mediawik Wiki site, just go into the css page and modify it as follows:

.pBody {
font-size: 95%;
background-color: white;
color: black;
border-collapse: collapse;
border: 1px solid #aaa;
padding: 0 .8em .3em .5em;
display:none;
}

Of course, it is the display:none; that removes them from the display. They are still there, you just can’t see them anymore.