repr: update docstring for possible values of the context argument (J…

…uliaLang#39795)

base/strings/io.jl

@@ -249,14 +249,18 @@ print(io::IO, s::Union{String,SubString{String}}) = (write(io, s); nothing)
 Create a string from any value using the [`show`](@ref) function.
 You should not add methods to `repr`; define a `show` method instead.
 
-The optional keyword argument `context` can be set to an `IO` or [`IOContext`](@ref)
-object whose attributes are used for the I/O stream passed to `show`.
+The optional keyword argument `context` can be set to a `:key=>value` pair, a
+tuple of `:key=>value` pairs, or an `IO` or [`IOContext`](@ref) object whose
+attributes are used for the I/O stream passed to `show`.
 
 Note that `repr(x)` is usually similar to how the value of `x` would
 be entered in Julia. See also [`repr(MIME("text/plain"), x)`](@ref) to instead
 return a "pretty-printed" version of `x` designed more for human consumption,
 equivalent to the REPL display of `x`.
 
+!!! compat "Julia 1.7"
+ Passing a tuple to keyword `context` requires Julia 1.7 or later.
+
 # Examples
 ```jldoctest
 julia> repr(1)