doc: remind users that versioninfo may include secrets (JuliaLang#43839)

Add a warning to the docstring of `InteractiveUtils.versioninfo()`
reminding users to remove sensitive information before sharing the
output text.

stdlib/InteractiveUtils/src/InteractiveUtils.jl

@@ -85,6 +85,10 @@ controlled with boolean keyword arguments:
 
 - `verbose`: print all additional information
 
+!!! warning "Warning"
+    The output of this function may contain sensitive information. Before sharing the output,
+    please review the output and remove any data that should not be shared publicly.
+
 See also: [`VERSION`](@ref).
 """
 function versioninfo(io::IO=stdout; verbose::Bool=false)