Fix shadow bin argument passing - args were shifted incorrectly

The shadow-bin/npm and shadow-bin/npx files were incorrectly passing the
bin name ('npm'/'npx') as the first argument, which caused args to be
set to a string instead of an array. This resulted in 'findLast is not
a function' errors because strings don't have the findLast method.

- shadow-bin/npm: Remove 'npm' argument (already hardcoded in shadowNpmBin)
- shadow-bin/npx: Use correct shadowNpxBin function and remove 'npx' argument

Fixes #911

Author: jdalton

shadow-bin/npm

@@ -11,7 +11,7 @@ void (async () => {
 
   process.exitCode = 1
 
-  const { spawnPromise } = await shadowNpmBin('npm', process.argv.slice(2), { stdio: 'inherit' })
+  const { spawnPromise } = await shadowNpmBin(process.argv.slice(2), { stdio: 'inherit' })
 
   // See https://nodejs.org/api/child_process.html#event-exit.
   spawnPromise.process.on('exit', (code, signalName) => {

shadow-bin/npx

@@ -7,11 +7,11 @@ void (async () => {
   const rootPath = path.join(__dirname, '..')
   Module.enableCompileCache?.(path.join(rootPath, '.cache'))
 
-  const shadowNpmBin = require(path.join(rootPath, 'dist/shadow-npm-bin.js'))
+  const shadowNpxBin = require(path.join(rootPath, 'dist/shadow-npx-bin.js'))
 
   process.exitCode = 1
 
-  const { spawnPromise } = await shadowNpmBin('npx', process.argv.slice(2), { stdio: 'inherit' })
+  const { spawnPromise } = await shadowNpxBin(process.argv.slice(2), { stdio: 'inherit' })
 
   // See https://nodejs.org/api/child_process.html#event-exit.
   spawnPromise.process.on('exit', (code, signalName) => {