Fix missing word in RFC 3543

Under "future possibilities", a sentence was missing the word
"crate".  Let's fix that.

Author: traviscross

text/3543-patchable-function-entry.md

@@ -262,7 +262,7 @@ Disadvantages:
 # Future possibilities
 [future-possibilities]: #future-possibilities
 
-We could potentially use these for dynamic tracing of rust programs, similar to `#[instrument]` in the `tracing` today, but with more configurable behavior and even lower overhead (since there will be no conditionals to check, just a nop sled to go down).
+We could potentially use these for dynamic tracing of rust programs, similar to `#[instrument]` in the `tracing` crate today, but with more configurable behavior and even lower overhead (since there will be no conditionals to check, just a nop sled to go down).
 
 We could consider adding `#[unpatchable]` as a shorthand for `#[patchable_function_entry(entry_nops = 0, prefix-nops = 0)]`.