Fix type checking for qualified id block parameters.

[chatwyn]

Hi:
we're in the process of testing with Clang 10 and noticed a behavior change caused by this commit.

Consider the following piece of code:

@protocol P
@end

@protocol Q
@end

@interface I <P,Q>
@end

void a() {
    void (^genericBlockWithParam)(id <P>);
    void (^blockWithParam)(I *);
    blockWithParam = genericBlockWithParam;
    genericBlockWithParam = blockWithParam;
}

when I use clang 9, it will be below error

incompatible block pointer types assigning to 'void (^__strong)(I *__strong)' from 'void (^__strong)(__strong id<P>)'
    blockWithParam = genericBlockWithParam;
                   ^ ~~~~~~~~~~~~~~~~~~~~~

but in clang 10, the error is that

incompatible block pointer types assigning to 'void (^__strong)(__strong id<P>)' from 'void (^__strong)(I *__strong)'
     genericBlockWithParam = blockWithParam;
                    ^ ~~~~~~~~~~~~~~~~~~~~~

I think clang 9 is reasonable.

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