docs/multi-thread-compression: Fix wrong command string

s/info_migrate_capabilities/info migrate_capabilities

Signed-off-by: Wei Jiangang <weijg.fnst@cn.fujitsu.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Liang Li <liang.z.li@intel.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

docs/multi-thread-compression.txt

@@ -110,7 +110,7 @@ Usage
 =====
 1. Verify both the source and destination QEMU are able
 to support the multiple thread compression migration:
-    {qemu} info_migrate_capabilities
+    {qemu} info migrate_capabilities
     {qemu} ... compress: off ...
 
 2. Activate compression on the source: