Fix test failure in TestSoftDeletesDirectoryReaderWrapper on expected number of deletes

[cwperks]

Description

This PR fixes TestSoftDeletesDirectoryReaderWrapper.testAvoidWrappingReadersWithoutSoftDeletes which consistently fails with a reproducible seed:

./gradlew test --tests TestSoftDeletesDirectoryReaderWrapper.testAvoidWrappingReadersWithoutSoftDeletes -i \
-Dtests.seed=CB973876C2F6A82A \
-Dtests.locale=fr-SN \
-Dtests.timezone=Etc/GMT+7 \
-Dtests.asserts=true \
-Dtests.file.encoding=UTF-8

Thank you to @easyice for the suggested solution and pointers for this fix. For more details about the test failure see: #14020 (comment)

Resolves: #14020