fix #38897, docstring for .op= (#38898)

Also change "equivalent to" to a more rough "akin to" since `x .op y` isn't always identical to `broadcast(op, x, y)`.

(cherry picked from commit 74a08fe)

stdlib/REPL/src/docview.jl

@@ -219,12 +219,14 @@ function lookup_doc(ex)
  end
  if isa(ex, Symbol) && Base.isoperator(ex)
  str = string(ex)
+ isdotted = startswith(str, ".")
  if endswith(str, "=") && Base.operator_precedence(ex) == Base.prec_assignment
  op = str[1:end-1]
- return Markdown.parse("`x $op= y` is a synonym for `x = x $op y`")
- elseif startswith(str, ".")
+ eq = isdotted ? ".=" : "="
+ return Markdown.parse("`x $op= y` is a synonym for `x $eq x $op y`")
+ elseif isdotted
  op = str[2:end]
- return Markdown.parse("`x $ex y` is equivalent to `broadcast($op, x, y)`. See [`broadcast`](@ref).")
+ return Markdown.parse("`x $ex y` is akin to `broadcast($op, x, y)`. See [`broadcast`](@ref).")
  end
  end
  binding = esc(bindingexpr(namify(ex)))