Here's one way...
Put the following into a tiddler to create a button. Then click the button:
<$button> remove "=="
<$list filter="[all[tiddlers]!is[system]search:text[==]] -[<currentTiddler>]">
<$action-setfield text={{{ [<currentTiddler>get[text]split[==]join[]] }}} />
</$list>
</$button>
Notes:
1) The $list filter finds every tiddler that contains at least one occurrence of "==" (excluding the tiddler containing the button itself)
2) For each tiddler found, it gets the text content, splits it at each occurrence of "==" (removing the "==" in the process), and then joins the remaining text
3) It then replaces the original text content with the re-assembled text without the "=="
Be sure to backup your document before trying this, as it can change lots of tiddlers with a single click!
enjoy,
-e