doc: minor correction to note on process section

[danbev]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

doc

[gireeshpunathil]

almost like a typo correction, land-able in few hours.

[gireeshpunathil]

CI: https://ci.nodejs.org/job/node-test-pull-request/10847/

[benjamingr]

Arm-fanned CI failure unrelated, we can land this.

not ok 272 sequential/test-make-doc
  ---
  duration_ms: 1.32
  severity: fail
  stack: |-
    fs.js:924
      return binding.readdir(pathModule.toNamespacedPath(path), options.encoding);
                     ^
    
    Error: ENOENT: no such file or directory, scandir '/home/iojs/build/workspace/node-test-binary-arm/out/doc/api'
        at Object.fs.readdirSync (fs.js:924:18)
        at Object.<anonymous> (/home/iojs/build/workspace/node-test-binary-arm/test/sequential/test-make-doc.js:15:17)
        at Module._compile (module.js:607:30)
        at Object.Module._extensions..js (module.js:618:10)
        at Module.load (module.js:526:32)
        at tryModuleLoad (module.js:489:12)
        at Function.Module._load (module.js:481:3)
        at Function.Module.runMain (module.js:648:10)
        at startup (bootstrap_node.js:191:16)
        at bootstrap_node.js:609:3
  ...

[gireeshpunathil]

Landed in 35deef0