Use 'ggplot2::annotate' for single annotation (#902)

# Pull Request

- Fixes #901

### Changes description

- Annotation plotted only once
- Correct expression

<img width="870" height="560" alt="image"
src="https://github.com/user-attachments/assets/8ca0b0db-5d97-45d4-8247-4db113e1eaa9"
/>

Co-authored-by: Marcin <[email protected]>

Author: averissimo

R/tm_a_regression.R

@@ -830,18 +830,15 @@ srv_a_regression <- function(id,
               color = "red",
               linetype = "dashed"
             ) +
-            ggplot2::geom_text(
-              ggplot2::aes(
-                x = 0,
-                y = mean(data$.cooksd, na.rm = TRUE),
-                label = paste("mu", "=", round(mean(data$.cooksd, na.rm = TRUE), 4)),
-                vjust = -1,
-                hjust = 0,
-                color = "red",
-                angle = 90
-              ),
-              parse = TRUE,
-              show.legend = FALSE
+            ggplot2::annotate(
+              geom = "text",
+              x = 0,
+              y = mean(data$.cooksd, na.rm = TRUE),
+              label = paste("mu", "=", round(mean(data$.cooksd, na.rm = TRUE), 4)),
+              vjust = -1,
+              hjust = 0,
+              color = "red",
+              angle = 90
             ) +
             outlier_label,
           env = list(plot = plot, outlier = input$outlier, outlier_label = outlier_label())