Update benchmark.asciidoc

Fixed incorrect parameter spec for benchmark nodes

docs/reference/search/benchmark.asciidoc

@@ -13,12 +13,12 @@ measuring their performance relative to one another.
 
 [IMPORTANT]
 =====
-To be eligible to run benchmarks nodes must be started with: *--node.bench=true*. This is just a way to mark certain nodes as "executors". Searches will still be distributed out to the cluster in the normal manner. This is primarily a defensive measure to prevent production nodes from being flooded with potentially many requests. Typically one would start a single node with this setting and submit benchmark requests to it.
+To be eligible to run benchmarks nodes must be started with: `--node.bench true`. This is just a way to mark certain nodes as "executors". Searches will still be distributed out to the cluster in the normal manner. This is primarily a defensive measure to prevent production nodes from being flooded with potentially many requests. Typically one would start a single node with this setting and submit benchmark requests to it.
 =====
 
 [source,bash]
 --------------------------------------------------
-$ ./bin/elasticsearch --node.bench=true
+$ ./bin/elasticsearch --node.bench true
 --------------------------------------------------
 
 Benchmarking a search request is as simple as executing the following command: