MDEV-22114 Assertion failure on SET GLOBAL innodb_buffer_pool_evict='uncompressed'

innodb_buffer_pool_evict_uncompressed(): Remove the mutex acquisition
that was inadvertently added in 1a6f708e.

mysql-test/suite/sys_vars/r/innodb_buffer_pool_evict_basic.result

 SELECT @@global.innodb_buffer_pool_evict;
 @@global.innodb_buffer_pool_evict
 
+CREATE TABLE t(a INT) ENGINE=InnoDB ROW_FORMAT=COMPRESSED;
 SET GLOBAL innodb_buffer_pool_evict = 'uncompressed';
 SELECT @@global.innodb_buffer_pool_evict;
 @@global.innodb_buffer_pool_evict
 
+DROP TABLE t;

mysql-test/suite/sys_vars/t/innodb_buffer_pool_evict_basic.test

@@ -4,7 +4,9 @@
 
 SELECT @@global.innodb_buffer_pool_evict;
 
+CREATE TABLE t(a INT) ENGINE=InnoDB ROW_FORMAT=COMPRESSED;
 SET GLOBAL innodb_buffer_pool_evict = 'uncompressed';
 
 # Should always be empty.
 SELECT @@global.innodb_buffer_pool_evict;
+DROP TABLE t;

storage/innobase/handler/ha_innodb.cc

@@ -18279,10 +18279,8 @@ innodb_buffer_pool_evict_uncompressed()
 		ut_ad(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);
 		ut_ad(block->in_unzip_LRU_list);
 		ut_ad(block->page.in_LRU_list);
-		mutex_enter(&block->mutex);
 
 		if (!buf_LRU_free_page(&block->page, false)) {
-			mutex_exit(&block->mutex);
 			all_evicted = false;
 		}
 		block = prev_block;