fix: inconsistent kernel version for julia (#1623)

Author: mcanouil

docs/computations/julia.qmd

@@ -152,12 +152,12 @@ Alternatively, if you are using Jupyter from within any other version of Python
 
 ### Kernel Selection
 
-You'll note in our first example that we specified the use of the `julia-1.7` kernel explicitly in our document options (shortened for brevity):
+You'll note in our first example that we specified the use of the `julia-1.8` kernel explicitly in our document options (shortened for brevity):
 
 ``` markdown
 ---
 title: "StatsPlots Demo"
-jupyter: julia-1.7
+jupyter: julia-1.8
 ---
 ```