Remove   in post content

As per comments on the original post, it appears this is as a result of copying text from another source.

Unfortunately, copying and pasting can bring across whatever junk the source editor decides to include. MS Word has typically been terrible at this; WordPress now does a pretty good job at cleaning it up but it’s not always perfect.

Rather than pasting directly, I’d suggest using the “Paste as Text” button on the WordPress editor toolbar (it looks like a T on a clipboard, next to the text colour option):

Paste as text toolbar button

Alternatively, pasting the text into a text-only editor such as Notepad before copying it again and then pasting into WordPress will also do the trick.