.python/SpellCheck: Increase SpellCheck plugin max failures
    
    REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2593
    
    Increases the maximum number of failures in the SpellCheck plugin so
    that more issues can be caught in a single pass.
    
    Cc: Bob Feng <bob.c.feng@intel.com>
    Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
    Cc: Liming Gao <liming.gao@intel.com>
    Cc: Michael D Kinney <michael.d.kinney@intel.com>
    Cc: Sean Brogan <sean.brogan@microsoft.com>
    Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
    Reviewed-by: Sean Brogan <sean.brogan@microsoft.com>
    Reviewed-by: Shenglei Zhang <shenglei.zhang@intel.com>