Fix percentage formatting in top n regression and improvement tables (#…

…77)

In the release candidate report
[here](http://crossbow.voltrondata.com/release_reports/arrow-release-report-15.0.0-rc1.html),
there was an bug in {gt} code that was causing pre-computed percentages
to be multiplied by an additional 100x. This PR tells {gt} that they are
already percentages.

FYI @raulcd @assignUser

performance-release-report/R/functions.R

@@ -205,7 +205,7 @@ top_zscore_table <- function(.data, top_n = 20, direction = c("improvement", "re
     arrange(language, suite, name, params) %>%
     gt(rowname_col = "language", groupname_col = "suite") %>%
     fmt_markdown(columns = "name") %>%
-    fmt_percent(columns = "analysis_pairwise_percent_change", decimals = 0) %>%
+    fmt_percent(columns = "analysis_pairwise_percent_change", scale_values = FALSE, decimals = 2) %>%
     fmt_number(columns = ends_with("single_value_summary"), decimals = 0) %>%
     fmt_number(columns = "analysis_lookback_z_score_z_score", decimals = 2) %>%
     cols_label(