Make autolimits! default to current_axis() (#3469)

* Default to current_axis()

This PR makes `Makie.autolimits!` default to using `current_axis()`

* Check is current_axis returns nothing

* Actually call autolimits on curr_ax

src/makielayout/blocks/axis.jl

@@ -898,14 +898,21 @@ function update_linked_limits!(block_limit_linking, xaxislinks, yaxislinks, tlim
 end
 
 """
+    autolimits!()
     autolimits!(la::Axis)
 
 Reset manually specified limits of `la` to an automatically determined rectangle, that depends on the data limits of all plot objects in the axis, as well as the autolimit margins for x and y axis.
+The argument `la` defaults to `current_axis()`.
 """
 function autolimits!(ax::Axis)
     ax.limits[] = (nothing, nothing)
     return
 end
+function autolimits!()
+    curr_ax = current_axis()
+    isnothing(curr_ax)  &&  throw(ArgumentError("Attempted to call `autolimits!` on `current_axis()`, but `current_axis()` returned nothing."))
+    autolimits!(curr_ax)
+end
 
 function autolimits(ax::Axis, dim::Integer)
     # try getting x limits for the axis and then union them with linked axes