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There is indeed no fastcgi_params_hash_max_size and fastcgi_params_hash_bucket_size directives. This error message is "automatic" in a way that it takes the hash name (in this case fastcgi_params_hash) then constructs suggested directive names by appending _max_size and _bucket_size.

The NGINX hashes in general are used to store array-like configuration data like maps or fastcgi_paramss (your case), and there is separate document about them having to say:

Most hashes have the corresponding directives that allow changing these parameters, for example, for the server names hash they are server_names_hash_max_size and server_names_hash_bucket_size.

So your hash does not have the "corresponding directives" and there is nothing you can do aside from:

• Investigate why you have too many fastcgi_param directives in your configuration? (or with too much lengthy values). It very likely that you have suboptimal configuration in regards with fastcgi_paramss. Remember, those are passed to FastCGI (e.g. PHP-FPM), and if that data is too big, then you sure to experience performance issues simply because of much data going through between NGINX-PHP-FPM.
• File a bug issue with NGINX about adding these directives