Update ext/DynamicPPLTestExt/sampler.jl

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: penelopeysm

ext/DynamicPPLTestExt/sampler.jl

@@ -8,7 +8,8 @@
 
 Return the mean of variable represented by `varname` in `chain`.
 """
-DynamicPPL.TestUtils.marginal_mean_of_samples(chain, varname) = mean(Array(chain[Symbol(varname)]))
+DynamicPPL.TestUtils.marginal_mean_of_samples(chain, varname) =
+    mean(Array(chain[Symbol(varname)]))
 
 """
     test_sampler(models, sampler, args...; kwargs...)