Update iRBC removal parameters and plot

The delta_iS parameter is defined in terms of delta_iR and a scaling
parameter, but this was not evident in the model description.

vignettes/articles/model-description.Rmd

@@ -603,11 +603,13 @@ The removal rate \(\delta_i\) of infected RBCs from the circulation into the spl
     \Icnet[-1]^{g_d^U} + \left(\delta_{50}^I \cdot \left[
       \Icnet[-1] + \Ucnet[-1]
     \right]\right)^{g_d^U}
-  }
+  } \\
+  \delta_{iS} &= \delta_{iR} \cdot k_{iS}
 \end{align}
 
 | Symbol             | Description                  | Baseline value          |
 |--------------------|------------------------------|-------------------------|
+| \(k_{iS}\)         | Schizont scaling parameter   | \(`r p$delta_iS_scale`\)|
 | \(\delta_{iR}\)    | **Pf** ring removal rate     | \(`r p$delta_iR`\)      |
 | \(\delta_{iS}\)    | **Pf** schizont removal rate | \(`r p$delta_iS`\)      |
 | \(\delta_{iR}\)    | **Pv** ring removal rate     | \(`r pv$delta_iR`\)     |
@@ -637,7 +639,7 @@ ggplot(df_di1, aes(age, value)) +
   xlab("iRBC age (hours)") +
   scale_y_continuous(
     name = "Removal rate (unscaled)",
-    breaks = c(0.15, 0.30),
+    breaks = c(p$delta_iR, p$delta_iS),
     labels = c(expression(delta[iR]), expression(delta[iS]))
   )
 ```