Remove numbers from requirements

Author: ecstatic-morse

promotion.md

@@ -12,7 +12,7 @@ arithmetic.
 
 ## Rules
 
-### 1. Panics
+### Panics
 
 Promotion is not allowed to throw away side effects.  This includes panicking.
 Let us look at what happens when we promote `&(0_usize - 1)` in a debug build:
@@ -46,7 +46,7 @@ earlier version of miri used to panic on arithmetic overflow even in release
 mode.  This breaks promotion, because now promoting code that would work (and
 could not panic!) at run-time leads to a compile-time CTFE error.
 
-### 2. Const safety
+### Const safety
 
 We have explained what happens when evaluating a promoted panics, but what about
 other kinds of failure -- what about hitting an unsupported operation or
@@ -89,13 +89,13 @@ but to abort compilation of a program that would have compiled fine if we would
 not have decided to promote.  It is the responsibility of `foo` to not fail this
 way when working with const-safe arguments.
 
-### 3. Constraints on constants
+### Constraints on constants
 
 All the [extra restrictions for constants](const.md) beyond const safety also
 apply to promoteds, for the same reason: Evaluating the expression at
 compile-time instead of run-time should not alter program behavior.
 
-### 4. Drop
+### Drop
 
 Expressions containing "needs drop" types
 can never be promoted. If such an expression were promoted, the `Drop` impl would