fix missing h3 tag (from CRAN results)

R/proj_crs_text.R

@@ -9,7 +9,7 @@
 #' See the [library documentation](https://proj.org/development/reference/functions.html#transformation-setup)
 #' for details on input and output formats.
 #'
-#' @section: warning
+#' @section Warning:
 #' Note that a PROJ string is not a full specification, in particular this means that a string like "+proj=laea" cannot be converted
 #' to full WKT, because it is technically a transformation step not a crs. To get the full WKT form use a string like "+proj=laea +type=crs".
 #' @export