Fix pecl distro

[tony2001]

Latest protobuf version from PECL fails to build because of missing file wkt.inc.
This patch adds it to the tar archive.

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[tony2001]

@googlebot I signed it!

[acozzette]

@tony2001 Thank you for the fix but I believe this issue has already been fixed in #8022.

[tony2001]

Looks like it was, indeed.
Ok, waiting for the new version then.