REPL doc lookup assumed ASCII for the given string, fixes #41589 (#41594)

(cherry picked from commit be443ac)

Author: Seelengrab

stdlib/REPL/src/docview.jl

@@ -221,7 +221,7 @@ function lookup_doc(ex)
         str = string(ex)
         isdotted = startswith(str, ".")
         if endswith(str, "=") && Base.operator_precedence(ex) == Base.prec_assignment && ex !== :(:=)
-            op = str[1:end-1]
+            op = chop(str)
             eq = isdotted ? ".=" : "="
             return Markdown.parse("`x $op= y` is a synonym for `x $eq x $op y`")
         elseif isdotted && ex !== :(..)

stdlib/REPL/test/docview.jl

@@ -27,3 +27,7 @@ end
     # https://github.com/JuliaLang/julia/issues/37757
     @test REPL.insert_hlines(IOBuffer(), nothing) === nothing
 end
+
+@testset "Unicode doc lookup (#41589)" begin
+    @test REPL.lookup_doc(:(÷=)) isa Markdown.MD
+end