doc: doc-tests in bytes/mod.rs and character/mod.rs should not reference functions from submodules

[DanikVitek]

These modules provide universal implementation of the parser combinators. Meanwhile, complete and streaming submodules provide the particular implementations, which might potentially be different from universal (implemented manually/inlined), rather than reference a universal implementation.
Therefore, the doc tests neither perform checks of the universal implementations, nor they show how to use the universal implementation.

For instance:

nom/src/bytes/mod.rs

Line 34 in a44b52e

/// use nom::bytes::streaming::tag;

nom/src/bytes/mod.rs

Line 102 in a44b52e

/// use nom::bytes::streaming::tag_no_case;

nom/src/character/mod.rs

Line 90 in a44b52e

/// # use nom::character::streaming::char;

nom/src/character/mod.rs

Line 147 in a44b52e

/// # use nom::character::complete::satisfy;