fix block_job_set_speed name in documentation

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index a6f5a84..461fa59 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -92,8 +92,8 @@
     },
 
 STEXI
-@item block_job_set_stream
-@findex block_job_set_stream
+@item block_job_set_speed
+@findex block_job_set_speed
 Set maximum speed for a background block operation.
 ETEXI