CWG-D043: Disable a rect pruning condition when H_PART is on

The original condition only applied to 3-way partition to reduce syntax
redundancy. This commit moves it under `!CONFIG_H_PART` flag.

Performance
| CONFIG |   PSNR   | Enc Time | Dec Time |
| :----: | :------: | :------: | :------: |
|   AI   |  -0.17%  |   110%   |   101%   |
|   RA   |  -0.12%  |   102%   |   101%   |
|   LD   |  -0.15%  |   102%   |   102%   |
|   F1   |  -0.13%  |   109.3% |   100.8% |
|   F2   |  -0.11%  |   110.0% |   100.4% |
|   AS   |  -0.08%  |   101.2% |    99.9% |

STATS_CHANGED
diff --git a/av1/encoder/partition_search.c b/av1/encoder/partition_search.c
index 9787a8e..dc0c788 100644
--- a/av1/encoder/partition_search.c
+++ b/av1/encoder/partition_search.c
@@ -3693,15 +3693,14 @@
                               mi_pos_rect[i][0][i]))
       continue;
 
-#if CONFIG_EXT_RECUR_PARTITIONS
+#if CONFIG_EXT_RECUR_PARTITIONS && !CONFIG_H_PARTITION
     if (pc_tree->parent) {
       if ((pc_tree->parent->horizontal3[1] == pc_tree && i == HORZ) ||
           (pc_tree->parent->vertical3[1] == pc_tree && i == VERT)) {
         continue;
       }
     }
-
-#endif  // CONFIG_EXT_RECUR_PARTITIONS
+#endif  // CONFIG_EXT_RECUR_PARTITIONS && !CONFIG_H_PARTITION
 
     // Sub-partition idx.
     const PARTITION_TYPE partition_type = rect_partition_type[i];
@@ -3722,6 +3721,7 @@
     }
 
     PC_TREE **sub_tree = (i == HORZ) ? pc_tree->horizontal : pc_tree->vertical;
+    assert(sub_tree);
 
     const int num_planes = av1_num_planes(cm);
     for (int idx = 0; idx < SUB_PARTITIONS_RECT; idx++) {