[src/global.rs] Get cargo test --all-features to pass

[SamuelMarks]

Before:

$ cargo test --all-features

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s


running 1 test
test src/global.rs - global::GenerationConfig::options (line 394) ... FAILED

failures:

---- src/global.rs - global::GenerationConfig::options (line 394) stdout ----
�[0m�[1m�[38;5;9merror[E0063]�[0m�[0m�[1m: missing field `diesel_backend` in initializer of `GenerationConfig<'_>`�[0m
�[0m �[0m�[0m�[1m�[38;5;12m--> �[0m�[0msrc/global.rs:397:1�[0m
�[0m  �[0m�[0m�[1m�[38;5;12m|�[0m
�[0m�[1m�[38;5;12m6�[0m�[0m �[0m�[0m�[1m�[38;5;12m|�[0m�[0m �[0m�[0mGenerationConfig {�[0m
�[0m  �[0m�[0m�[1m�[38;5;12m|�[0m�[0m �[0m�[0m�[1m�[38;5;9m^^^^^^^^^^^^^^^^�[0m�[0m �[0m�[0m�[1m�[38;5;9mmissing `diesel_backend`�[0m

�[0m�[1m�[38;5;9merror[E0063]�[0m�[0m�[1m: missing field `diesel_backend` in initializer of `GenerationConfig<'_>`�[0m
�[0m  �[0m�[0m�[1m�[38;5;12m--> �[0m�[0msrc/global.rs:403:1�[0m
�[0m   �[0m�[0m�[1m�[38;5;12m|�[0m
�[0m�[1m�[38;5;12m12�[0m�[0m �[0m�[0m�[1m�[38;5;12m|�[0m�[0m �[0m�[0mGenerationConfig {�[0m
�[0m   �[0m�[0m�[1m�[38;5;12m|�[0m�[0m �[0m�[0m�[1m�[38;5;9m^^^^^^^^^^^^^^^^�[0m�[0m �[0m�[0m�[1m�[38;5;9mmissing `diesel_backend`�[0m

�[0m�[1m�[38;5;9merror�[0m�[0m�[1m: aborting due to 2 previous errors�[0m

�[0m�[1mFor more information about this error, try `rustc --explain E0063`.�[0m
Couldn't compile the test.

failures:
    src/global.rs - global::GenerationConfig::options (line 394)

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.02s

After:

$ cargo test --all-features
running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s


running 1 test
test src/global.rs - global::GenerationConfig::options (line 394) ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.18s

[hasezoey]

This change makes it only run with feature advanced-queries.
I made #148 to run in both conditions while also removing a wrong documentation entry, are you fine with that?

[SamuelMarks]

As long as cargo test --all-features passes I'm happy

(I always run cargo make on Rust projects and it was complaining when it got to that default task)