Revert "Don't blacklist 507 Insufficent Storage #5346 (#5424)"

This reverts commit e1f5a49c21826590811710f73e37b7b72e256960.

Retrying uploads with insufficent storage errors frequently leads to
high server traffic. See #5537 for links and a sketch of a correct
solution.

src/libsync/syncjournalfilerecord.cpp

@@ -131,7 +131,6 @@ SyncJournalErrorBlacklistRecord SyncJournalErrorBlacklistRecord::update(
     bool mayBlacklist =
             item._errorMayBeBlacklisted  // explicitly flagged for blacklisting
             || (item._httpErrorCode != 0 // or non-local error
-                && item._httpErrorCode != 507 // Don't blacklist "Insufficient Storage"
 #ifdef OWNCLOUD_5XX_NO_BLACKLIST
                 && item._httpErrorCode / 100 != 5 // In this configuration, never blacklist error 5xx
 #endif