MDEV-24188 fixup: Correct the FindBlockX predicate

FindBlockX::operator(): Return false if an x-latched block is found.
Previously, we were incorrectly returning false if the block was in
the log, only if not x-latched.

It is unknown if this mistake had any visible impact. Often,
we would register both MTR_MEMO_BUF_FIX and MTR_MEMO_PAGE_X_FIX
for the same block.

storage/innobase/mtr/mtr0mtr.cc

@@ -804,7 +804,7 @@ mtr_t::release_free_extents(ulint n_reserved)
   space->release_free_extents(n_reserved);
 }
 
-/** Find out whether a block was X-latched by the mini-transaction */
+/** Find out whether a block was not X-latched by the mini-transaction */
 struct FindBlockX
 {
   const buf_block_t █
@@ -814,7 +814,7 @@ struct FindBlockX
   /** @return whether the block was not found x-latched */
   bool operator()(const mtr_memo_slot_t *slot) const
   {
-    return slot->object != &block || slot->type == MTR_MEMO_PAGE_X_FIX;
+    return slot->object != &block || slot->type != MTR_MEMO_PAGE_X_FIX;
   }
 };