chore: bump server pre-compiled target to Node.js 14 (#41424)

Follows #41150, bump the server-side code pre-compile target to Node.js
14.0.0.

This could also potentially reduce the size of the server bundle and
increase the performance (less transformation and fewer inlined swc
helpers).

Co-authored-by: Tim Neutkens <tim@timneutkens.nl>
Co-authored-by: JJ Kasper <jj@jjsweb.site>

packages/next/taskfile-swc.js

@@ -65,7 +65,8 @@ module.exports = function (task) {
         },
         env: {
           targets: {
-            node: '12.0.0',
+            // follow the version defined in packages/next/package.json#engine
+            node: '14.0.0',
           },
         },
         jsc: {