Improve docs on ClassifyContext

Improve docs on `ClassifyContext` by doing:

- Separate brief doc line from the rest
- Use uniform backticks on opcodes

src/blockdata/opcodes.rs

@@ -660,8 +660,10 @@ impl fmt::Debug for All {
 }
 
 
-/// Classification context for the opcode. Some opcodes like `OP_RESERVED`
-/// abort the script in [`ClassifyContext::Legacy`] context, but will act as OP_SUCCESS in tapscript
+/// Classification context for the opcode.
+///
+/// Some opcodes like `OP_RESERVED` abort the script in [`ClassifyContext::Legacy`] context, but
+/// will act as `OP_SUCCESS` in tapscript.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub enum ClassifyContext {
     /// Opcode used in tapscript context