Add elasticsearch- prefix to CLI tool docs (elastic#101626)

The tools are called `elasticsearch-shard` and `elasticsearch-node` and
so on, but in the docs about their JVM options the `elasticsearch-`
prefix is omitted. This commit fixes that.

docs/reference/commands/cli-jvm-options.asciidoc

@@ -2,9 +2,10 @@
 [float]
 ==== JVM options
 
-CLI tools run with 64MB of heap. For most tools, this value is fine. However, if needed
-this can be overriden by setting the CLI_JAVA_OPTS environment variable. For example,
-the following increases the heap size used by the `pass:a[{tool-name}]` tool to 1GB.
+CLI tools run with 64MB of heap. For most tools, this value is fine. However, if
+needed this can be overriden by setting the `CLI_JAVA_OPTS` environment variable.
+For example, the following increases the heap size used by the
+`pass:a[elasticsearch-{tool-name}]` tool to 1GB.
 
 [source,shell,subs=attributes+]
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