The %2 looks like a gigo, you have seen %2 before? I can check for it easily. Preserving the Google quote string is, I think, preferable to deleting it. No opinion on the quote argument generally unless you have another idea for preserving the quote/keywords some other way.

I suspect that the %2 is a corruption of %22 the double quote character; support for that is shown in this edit where the %22 became %2.

If you must preserve the search terms, perhaps they can be put in an html comment prefixed with 'google books search string: ' or some-such; perhaps like this:
<!-- google books search string: '&dq=%22the+last+days+of+papal+rome%2' -->

But, I see no reason to keep the search string. If there is a page number that gets readers to the correct page, that is sufficient. If editors did not choose to quote from the source using |quote= or, better, <blockquote>...</blockquote>, a bot should not be second-guessing them and making up quotations that may or may not exist as quotable text in the source. For example, &dq=salafi+origins+Abduh from this citation at Salafi movement, does not exist (so says google) in the book. In this case, the search string appears to be a scattershot attempt to find some text in the book.

It will be disabled with the next batch.

The data is not lost it is saved on my computer should it need to be restored or used in some way in the future.