Make it clearer the settings go into the vm.args file

docs/configuration/optimizing_beam.md

@@ -29,6 +29,7 @@ Check your OS documentation to adopt a similar strategy on other platforms.
 
 Disable the busy-waiting
 
+**vm.args:**
 ```
 +sbwt none
 +sbwtdcpu none
@@ -39,6 +40,7 @@ Disable the busy-waiting
 
 Enable more busy waiting, increase the internal maximum limit of BEAM processes and ports
 
+**vm.args:**
 ```
 +P 16777216
 +Q 16777216