test: Expand boolean query proptest size

[stuhood]

Re-reading #2538, I noticed that the proptest's total document count was not large enough to exercise some of the constants -- for example, the buffered union HORIZON value.

Increasing the total document count (by repeating all unique permutations more times to reach a target size) exposes a failure which minimizes to:

Intersection(
    [
        Leaf {
            field_idx: 0,
        },
        Union(
            [
                Leaf {
                    field_idx: 2,
                },
                Leaf {
                    field_idx: 2,
                },
            ],
        ),
    ],
)

in:

   0: __rustc::rust_begin_unwind
             at /rustc/d7ea436a02d5de4033fcf7fd4eb8ed965d0f574c/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/d7ea436a02d5de4033fcf7fd4eb8ed965d0f574c/library/core/src/panicking.rs:75:14
   2: core::panicking::panic_const::panic_const_sub_overflow
             at /rustc/d7ea436a02d5de4033fcf7fd4eb8ed965d0f574c/library/core/src/panicking.rs:178:21
   3: tantivy::query::union::buffered_union::BufferedUnionScorer<TScorer,TScoreCombiner>::is_in_horizon
             at ./src/query/union/buffered_union.rs:128:19
   4: <tantivy::query::union::buffered_union::BufferedUnionScorer<TScorer,TScoreCombiner> as tantivy::docset::DocSet>::seek_into_the_danger_zone
             at ./src/query/union/buffered_union.rs:206:12
   5: <alloc::boxed::Box<TDocSet> as tantivy::docset::DocSet>::seek_into_the_danger_zone
             at ./src/docset.rs:216:9
   6: <tantivy::query::intersection::Intersection<TDocSet,TOtherDocSet> as tantivy::docset::DocSet>::advance
             at ./src/query/intersection.rs:118:20
   7: tantivy::docset::DocSet::fill_buffer
             at ./src/docset.rs:102:16
   8: tantivy::query::weight::for_each_docset_buffered
             at ./src/query/weight.rs:29:25
   9: <tantivy::query::boolean_query::boolean_weight::BooleanWeight<TScoreCombiner> as tantivy::query::weight::Weight>::for_each_no_score
             at ./src/query/boolean_query/boolean_weight.rs:343:17
  10: tantivy::collector::Collector::collect_segment
             at ./src/collector/mod.rs:198:17
  11: tantivy::core::searcher::Searcher::search_with_executor::{{closure}}
             at ./src/core/searcher.rs:231:17