doc: remove x86 from os.arch() options

It is not possible for `process.arch` (which comes from V8's
`target_arch`) to be `x86`.

Also updates `process.arch` to have the same information.

PR-URL: #17899
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

doc/api/os.md

@@ -31,11 +31,10 @@ added: v0.5.0
 * Returns: {string}
 
 The `os.arch()` method returns a string identifying the operating system CPU
-architecture *for which the Node.js binary was compiled*.
+architecture for which the Node.js binary was compiled.
 
 The current possible values are: `'arm'`, `'arm64'`, `'ia32'`, `'mips'`,
-`'mipsel'`, `'ppc'`, `'ppc64'`, `'s390'`, `'s390x'`, `'x32'`, `'x64'`,  and
-`'x86'`.
+`'mipsel'`, `'ppc'`, `'ppc64'`, `'s390'`, `'s390x'`, `'x32'`, and `'x64'`.
 
 Equivalent to [`process.arch`][].
 

doc/api/process.md

@@ -450,9 +450,11 @@ added: v0.5.0
 
 * {string}
 
-The `process.arch` property returns a String identifying the processor
-architecture that the Node.js process is currently running on. For instance
-`'arm'`, `'ia32'`, or `'x64'`.
+The `process.arch` property returns a string identifying the operating system CPU
+architecture for which the Node.js binary was compiled.
+
+The current possible values are: `'arm'`, `'arm64'`, `'ia32'`, `'mips'`,
+`'mipsel'`, `'ppc'`, `'ppc64'`, `'s390'`, `'s390x'`, `'x32'`, and `'x64'`.
 
 ```js
 console.log(`This processor architecture is ${process.arch}`);