update quick-xml to 0.25

[trinity-1686a]

quick-xml 0.23 and 0.24 were yanked following tafia/quick-xml#471. This break installation of grcov from crates.io directly (but not building from this repo thanks to Cargo.lock) with the following error:

$> cargo install grcov
    Updating crates.io index
  Installing grcov v0.8.11
error: failed to compile `grcov v0.8.11`, intermediate artifacts can be found at `/tmp/cargo-installo0bs24`

Caused by:
  failed to select a version for the requirement `quick-xml = "^0.23"`
  candidate versions found which didn't match: 0.25.0, 0.22.0, 0.21.0, ...
  location searched: crates.io index
  required by package `grcov v0.8.11`

This PR update quick-xml to 0.25 so it can build again with no Cargo.lock

Would it be possible to get a 0.8.12 after this get merged, so cargo install works again?

[calixteman]

LGTM. Thank you.

[marco-c]

v0.8.12 released and published!

[trinity-1686a]

thanks!