package/flann: bump to version 1.9.2

- lz4 is a mandatory dependency since
  https://github.com/flann-lib/flann/commit/df3fc59212660e43867cb85d5e557f5cae6d30d7
- Drop patch (not needed since
  https://github.com/flann-lib/flann/commit/86c92adbdea3e41d7ad371732cfe3b8231e0ecc6)
- PYTHON_EXECUTABLE can be dropped since
  https://github.com/flann-lib/flann/commit/5f4ac506323585c1f74ef57a73962beb887e3a3b

https://github.com/flann-lib/flann/blob/1.9.2/ChangeLog



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>