Avoid hidden lifetime parameters for latest Rust nightly

[weikengchen]

In the recent nightly, Debug trait's implementation now may need to add <'_>, as hidden lifetime parameters would now become a warning.

And it could be difficult for developers to find out why, as the code of Derivative is not exposed in the compiler's warnings.

warning: hidden lifetime parameters in types are deprecated
   --> ff/src/fields/macros.rs:96:9
    |
96  | /         /// Represents an element of the prime field F_p, where `p == P::MODULUS`.
97  | |         /// This type can represent elements in any field of size at most
98  | |         #[doc = $field_size]
99  | |         /// bits.
...   |
114 | |             pub PhantomData<P>,
115 | |         );
    | |__________^ expected named lifetime parameter

[weikengchen]

I will research a little bit to see how to fix the issue here.

What happens is the following: ryu and itoa increases their rustc minimal version in a recent release, while we still want Derivative to be only requiring >0.34

[weikengchen]

Ready for CI.

Added the following version limits to the dev_dependency to avoid an error in the CI test suite. Local github actions execution is passing.

# 1.0.73 requires itoa 1.0.0, which requires rustc 1.36, while our msrv is 1.34
serde_json = "=1.0.72"
itoa = "=0.4.3"
# 1.0.7 requires rustc 1.36, while our msrv is 1.34
ryu = "=1.0.6"

Note: It is very unlikely to pass the clippy check unless we change msrv.