Unable to update npm using `npm i -g npm`

Thanks for all the hard work on this plugin, it's been great for me!

I have an issue that I believe is partially related to WSL1 with Ubuntu 18.04. I'm unable to update npm using the built-in upgrade method of `npm i -g npm`.

I get the following stack trace:
```
npm ERR! code EACCES
npm ERR! syscall rename
npm ERR! path /home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/npm-80a480ea/node_modules/string-width
npm ERR! dest /home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/string-width-35f27461
npm ERR! errno -13
npm ERR! Error: EACCES: permission denied, rename '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/npm-80a480ea/node_modules/string-width' -> '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/string-width-35f27461'
npm ERR! [OperationalError: EACCES: permission denied, rename '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/npm-80a480ea/node_modules/string-width' -> '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/string-width-35f27461'] {
npm ERR! cause: [Error: EACCES: permission denied, rename '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/npm-80a480ea/node_modules/string-width' -> '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/string-width-35f27461'] {
npm ERR! errno: -13,
npm ERR! code: 'EACCES',
npm ERR! syscall: 'rename',
npm ERR! path: '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/npm-80a480ea/node_modules/string-width',
npm ERR! dest: '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/string-width-35f27461'
npm ERR! },
npm ERR! errno: -13,
npm ERR! code: 'EACCES',
npm ERR! syscall: 'rename',
npm ERR! path: '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/npm-80a480ea/node_modules/string-width',
npm ERR! dest: '/home/bleeds/.asdf/installs/nodejs/14.16.0/.npm/lib/node_modules/.staging/string-width-35f27461'
npm ERR! }
npm ERR!
npm ERR! The operation was rejected by your operating system.
npm ERR! It is likely you do not have the permissions to access this file as the current user
npm ERR!
npm ERR! If you believe this might be a permissions issue, please double-check the
npm ERR! permissions of the file and its containing directories, or try running
npm ERR! the command again as root/Administrator.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/bleeds/.npm/_logs/2021-03-31T18_46_57_862Z-debug.log
```

I also have Ubuntu 20 running on WSL2 and npm updates fine using asdf in that environment, both running the same nodejs version.

Does anyone have any ideas on what could be happening? Obviously, there is an issue with renaming the files. I did try restarting my computer and running only the WSL1 terminal.