[FIX] reqs.txt: bump psutil from 5.5.1 to 5.6.6

Bumps [psutil](https://github.com/giampaolo/psutil) from 5.5.1 to 5.6.6.
- [Release notes](https://github.com/giampaolo/psutil/releases)
- [Changelog](https://github.com/giampaolo/psutil/blob/master/HISTORY.rst)
- [Commits](https://github.com/giampaolo/psutil/compare/release-5.5.1...release-5.6.6)

The only API-incompatible change in 5.6 is the removal of memory_maps() on
OSX, which we aren't relying on at this point:
  https://github.com/giampaolo/psutil/blob/master/HISTORY.rst#560



closes odoo/odoo#47632

Original-signed-off-by: dependabot[bot] <support@github.com>
X-original-commit: a6026a4f
Signed-off-by: Olivier Dony (odo) <odo@openerp.com>

requirements.txt

@@ -24,7 +24,7 @@ passlib==1.7.1
 Pillow==5.4.1 ; python_version < '3.7' or sys_platform != 'win32'
 Pillow==6.1.0 ; sys_platform == 'win32' and python_version >= '3.7'
 polib==1.1.0
-psutil==5.5.1
+psutil==5.6.6
 psycopg2==2.7.7; sys_platform != 'win32' and python_version < '3.8'
 psycopg2==2.8.3; sys_platform == 'win32' or python_version >= '3.8'
 pydot==1.4.1