Remove statement that opt-level 0 turns on debug

See #9020 (comment)

Author: joshtriplett

src/doc/src/reference/profiles.md

@@ -41,7 +41,7 @@ rearrange the compiled code which may make it harder to use with a debugger.
 
 The valid options are:
 
-* `0`: no optimizations, also turns on [`cfg(debug_assertions)`](#debug-assertions).
+* `0`: no optimizations
 * `1`: basic optimizations
 * `2`: some optimizations
 * `3`: all optimizations