doc: revert file access in sliding.Rmd

Author: dshemetov

vignettes/articles/sliding.Rmd

@@ -68,7 +68,7 @@ versions for the less up-to-date input archive.
 ```{r grab-epi-data}
 theme_set(theme_bw())
 
-y <- readRDS(here::here("vignettes/articles/all_states_covidcast_signals.rds"))
+y <- readRDS("all_states_covidcast_signals.rds")
 y <- purrr::map(y, ~ select(.x, geo_value, time_value, version = issue, value))
 
 x <- epix_merge(