executor_linux: Remove unreachable PATH= code (#9778)

This has to have been unused because the HasPrefix operation is
backwards, meaning a Command.Env that includes PATH= never would have
worked; the default path was always used.

drivers/shared/executor/executor_linux.go

@@ -833,13 +833,7 @@ func lookupTaskBin(command *ExecCommand) (string, error) {
 		return "", fmt.Errorf("file %s not found under path %s", bin, taskDir)
 	}
 
-	// Find the PATH
 	path := "/usr/local/bin:/usr/bin:/bin"
-	for _, e := range command.Env {
-		if strings.HasPrefix("PATH=", e) {
-			path = e[5:]
-		}
-	}
 
 	return lookPathIn(path, taskDir, bin)
 }