Move back isascii() from Unicode to Base (#25076)

This function is not really Unicode-related and its definition does not depend
on the Unicode standard version. This fixes a bug introduced when moving
isascii() to Base.Unicode, as it was not exported from Unicode stdlib module
as it should have been.

Author: nalimilan

src/Distributed.jl

@@ -17,7 +17,7 @@ using Base: Process, Semaphore, JLOptions, AnyDict, buffer_writes, wait_connecte
             binding_module, notify_error, atexit, julia_exename, julia_cmd,
             AsyncGenerator, acquire, release, invokelatest,
             shell_escape_posixly, uv_error, coalesce, notnothing
-using Base.Unicode: isascii, isdigit, isnumeric
+using Base.Unicode: isdigit, isnumeric
 
 # NOTE: clusterserialize.jl imports additional symbols from Base.Serializer for use