plot_trajectoryX() looses arg 'value' for consistency with X API (#231)

`plot_trajectoryX()` looses the argument 'value' for consistency with X API

This is the opposite of what we discussed with Monika in our meeting, but
it makes makes more sense. When we discussed we didn't notice that the
X (thin) API does not have `main` or `value` -- only the Y (thick) API.
This is consistent with A/B testing two extreemes: thin and thick.

R/plot_trajectoryX.R

@@ -4,8 +4,6 @@
 #'   * The structure must be like [market_share].
 #'   * The following columns must have a single value: `sector`, `technology`,
 #'   `region`, `scenario_source`.
-#' @param main String of length 1. `metric` value to plot most prominently, as
-#'   the main trajectory line.
 #' @inheritParams prep_trajectoryY
 #' @inheritParams prep_timelineY
 #'
@@ -26,8 +24,13 @@
 #'     region == "global",
 #'     scenario_source == "demo_2020"
 #'   )
-#' plot_trajectoryX(data, main = "projected")
-plot_trajectoryX <- function(data, main = "projected", normalize = TRUE) {
+#' plot_trajectoryX(data)
+#'
+#' plot_trajectoryX(data, normalize = FALSE)
+plot_trajectoryX <- function(data, normalize = TRUE) {
+  stopifnot("projected" %in% tolower(data$metric))
+  main <- "projected"
+
   prep <- prep_trajectoryB(data, normalize = normalize)
 
   # FIXME: Make it work with values exposed to the user. Now it's not the case.

tests/testthat/test-plot_trajectoryX.R

@@ -7,6 +7,6 @@ test_that("outputs a ggplot", {
       scenario_source == "demo_2020"
     )
 
-  p <- plot_trajectoryX(data, main = "projected", normalize = TRUE)
+  p <- plot_trajectoryX(data, normalize = TRUE)
   expect_s3_class(p, "ggplot")
 })