Revert "feat: allow custom packageManager other than npm/yarn/p… (vuejs#4632)

This reverts commit e0f8469.

Author: haoqunjiang

packages/@vue/cli/lib/util/ProjectPackageManager.js

@@ -78,8 +78,6 @@ class PackageManager {
     if (!SUPPORTED_PACKAGE_MANAGERS.includes(this.bin)) {
       throw new Error(`Unknown package manager: ${this.bin}`)
     }
-
-    this.execBin = process.env.VUE_CLI_PACKAGE_MANAGER_BIN || this.bin
   }
 
   // Any command that implemented registry-related feature should support
@@ -164,7 +162,7 @@ class PackageManager {
 
   async install () {
     const args = await this.addRegistryToArgs(PACKAGE_MANAGER_CONFIG[this.bin].install)
-    return executeCommand(this.execBin, args, this.context)
+    return executeCommand(this.bin, args, this.context)
   }
 
   async add (packageName, isDev = true) {
@@ -173,7 +171,7 @@ class PackageManager {
       packageName,
       ...(isDev ? ['-D'] : [])
     ])
-    return executeCommand(this.execBin, args, this.context)
+    return executeCommand(this.bin, args, this.context)
   }
 
   async upgrade (packageName) {
@@ -194,15 +192,15 @@ class PackageManager {
       ...PACKAGE_MANAGER_CONFIG[this.bin].add,
       packageName
     ])
-    return executeCommand(this.execBin, args, this.context)
+    return executeCommand(this.bin, args, this.context)
   }
 
   async remove (packageName) {
     const args = [
       ...PACKAGE_MANAGER_CONFIG[this.bin].remove,
       packageName
     ]
-    return executeCommand(this.execBin, args, this.context)
+    return executeCommand(this.bin, args, this.context)
   }
 }