Revert certificates priority changes (EXPOSUREAPP-9277)

[SamuraiKek]

Not messing with the priorities anymore. Everything gets back to how it used to be.
As @mlenkeit mentioned in his last comment on the jira ticket: "the "good ol' priority should prioritize a 3/3 booster over a 2/2 VC as long as the date of the vaccination for the booster is after the 2/2 VC (which is fair to assume) (both are covered by the Series-completing Vaccination Certificate > 14 days)"

EDIT: this removes changes made to PersonCertificatesExtensions and PersonCertificatesExtensionsTest made in #4002, #4003 & #4005

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

100.0% Coverage
0.0% Duplication

[mtwalli]

Code is reverted to 2.8.0

• Booster is prioritised
  • cwa vc gen -s v.0.dn=3 v.0.sd=3 v.0.dt='2021-08-30' -e wru --seed mm -o
  • cwa vc gen -s v.0.dn=2 v.0.sd=2 v.0.dt='2021-08-26' -e wru --seed mm -o
  • cwa vc gen -s v.0.dn=1 v.0.sd=2 v.0.dt='2021-08-25' -e wru --seed mm -o

[jurajkusnier]

LGTM