test: accept upstream snapshot drift

* build-quarto-articles: pandoc added a default-styles comment header
  to its CSS output.
* build-reference: evaluate/knitr/rmarkdown now consumes two extra RNG
  draws before the example runs, shifting the output by two values.

Both are environmental drift, not behavioral changes from this PR.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: billdenney

tests/testthat/_snaps/build-quarto-articles.md

@@ -4,6 +4,9 @@
       cat(data$includes$style)
     Output
       
+          /* Default styles provided by pandoc.
+          ** See https://pandoc.org/MANUAL.html#variables-for-html for config info.
+          */
           code{white-space: pre-wrap;}
           span.smallcaps{font-variant: small-caps;}
           div.columns{display: flex; gap: min(4vw, 1.5em);}

tests/testthat/_snaps/build-reference.md

@@ -18,5 +18,5 @@
     Code
       cat(examples)
     Output
-      #> [1] 0.600760886 0.157208442 0.007399441 0.466393497 0.497777389
+      #> [1] 0.080750138 0.834333037 0.600760886 0.157208442 0.007399441