too many ways to do the same thing... drop support for #- in spin()

perhaps should drop `@knitr`, too...

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: knitr
 Type: Package
 Title: A General-Purpose Package for Dynamic Report Generation in R
-Version: 1.45.15
+Version: 1.45.16
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
     person("Abhraneel", "Sarma", role = "ctb"),

NEWS.md

@@ -38,6 +38,8 @@
 
 - The function `imgur_upload()` has been moved to (and enhanced in) the **xfun** package as `xfun::upload_imgur()` so it is no longer tied to **knitr** and can be reused by other pakages. Now `knitr::imgur_upload()` is only a wrapper function of `xfun::upload_imgur()`. You are recommended to use the latter (#2325).
 
+- `spin()` dropped support for `#-` as the chunk delimiter token. Please use `#+` or `# %%` or `#|` instead.
+
 # CHANGES IN knitr VERSION 1.45
 
 ## NEW FEATURES

R/spin.R

@@ -89,7 +89,7 @@ spin = function(
       block = strip_white(block) # rm white lines in beginning and end
       if (!length(block)) next
 
-      rc = '^(#|--)+(\\+|-| %%| ----+| @knitr)(.*?)\\s*-*\\s*$'
+      rc = '^(#|--)+(\\+| %%| ----+| @knitr)(.*?)\\s*-*\\s*$'
       j1 = grep(rc, block)
       # pipe comments (#|) should start a code chunk if they are not preceded by
       # chunk opening tokens