Add @eval using REPL to the atreplinit do block in REPL documentation. (#49717)

Author: kdheepak

stdlib/REPL/docs/src/index.md

@@ -623,6 +623,7 @@ It is possible to get an interface which is similar to the IPython REPL and the
 
 ```julia
 atreplinit() do repl
+    @eval import REPL
     if !isdefined(repl, :interface)
         repl.interface = REPL.setup_interface(repl)
     end