エラーの原因

kernel.php

Laravel7の場合

        'stateful_api' => [
            \App\Http\Middleware\EncryptCookies::class,
            \Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
            \Illuminate\Session\Middleware\StartSession::class,
            \Illuminate\View\Middleware\ShareErrorsFromSession::class,
            'throttle:60,1',
            'bindings',
        ],

Laravel8の場合
bindingsクラスをフルパスで記入する必要がある。
bindings →  \Illuminate\Routing\Middleware\SubstituteBindings::class

        'stateful_api' => [
            \App\Http\Middleware\EncryptCookies::class,
            \Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
            \Illuminate\Session\Middleware\StartSession::class,
            \Illuminate\View\Middleware\ShareErrorsFromSession::class,
            'throttle:60,1',
            \Illuminate\Routing\Middleware\SubstituteBindings::class,
        ],