[stable10] Add explicit PHPUnit asserts to unit tests flagged as 'risky' by PHPUnit6

[phil-davis]

Backport #34871

[codecov]

Codecov Report

Merging #34876 into stable10 will increase coverage by 0.27%.
The diff coverage is n/a.

@@              Coverage Diff               @@
##             stable10   #34876      +/-   ##
==============================================
+ Coverage       63.96%   64.23%   +0.27%     
  Complexity      19901    19901              
==============================================
  Files            1277     1277              
  Lines           76270    76270              
  Branches         1292     1292              
==============================================
+ Hits            48784    48993     +209     
+ Misses          27107    26898     -209     
  Partials          379      379

Flag	Coverage Δ	Complexity Δ
#javascript	53.2% <ø> (ø)	0 <ø> (ø)	⬇️
#phpunit	65.4% <ø> (+0.3%)	19901 <ø> (ø)	⬇️

Impacted Files	Coverage Δ	Complexity Δ
...eratedfilesharing/lib/Middleware/OcmMiddleware.php	77.27% <ø> (ø)	20 <0> (ø)	⬇️
lib/private/Share/Share.php	71.2% <0%> (+0.06%)	507% <0%> (ø)	⬇️
lib/private/Server.php	86.65% <0%> (+0.11%)	253% <0%> (ø)	⬇️
lib/private/DB/QueryBuilder/QueryBuilder.php	91.34% <0%> (+0.48%)	68% <0%> (ø)	⬇️
lib/private/DB/MDB2SchemaWriter.php	93.75% <0%> (+1.04%)	34% <0%> (ø)	⬇️
apps/files_trashbin/lib/Expiration.php	98.27% <0%> (+1.72%)	29% <0%> (ø)	⬇️
lib/private/DB/MDB2SchemaManager.php	91.22% <0%> (+1.75%)	17% <0%> (ø)	⬇️
lib/private/Files/Cache/Cache.php	97.61% <0%> (+1.79%)	110% <0%> (ø)	⬇️
lib/private/AllConfig.php	94.52% <0%> (+2.05%)	43% <0%> (ø)	⬇️
lib/private/Repair/RepairInvalidShares.php	100% <0%> (+2.73%)	17% <0%> (ø)	⬇️
... and 7 more

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[phil-davis]

PR in master has been approved and merged. This backport awaits approval.