Remove eval=TRUE override in RNA-seq vignette chunk

This chunk had eval=TRUE which overrode the global eval=FALSE guard,
causing pkgdown build to fail when DESeq2 is not available on CI.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: frenkiboy

vignettes/cacheR-rnaseq.Rmd

@@ -147,8 +147,8 @@ counts1 <- cached_read_counts(counts_dir, sample_table)
 
 # Second run: same arguments and same files → uses cache 
 
-```{r, eval=TRUE}
-counts2 <- cached_read_counts(counts_dir, sample_table) 
+```{r}
+counts2 <- cached_read_counts(counts_dir, sample_table)
 
 identical(counts1, counts2)
 ```