Fix date

Co-authored-by: Yuki Okushi <[email protected]>

Author: camelid

src/overview.md

@@ -262,7 +262,7 @@ Moreover, the compiler wasn't originally built to use a query system; the query
 system has been retrofitted into the compiler, so parts of it are not query-fied
 yet. Also, LLVM isn't our code, so that isn't querified either. The plan is to
 eventually query-fy all of the steps listed in the previous section,
-but as of <!-- date: 2021-11 --> February 2021, only the steps between HIR and
+but as of <!-- date: 2021-11 --> November 2021, only the steps between HIR and
 LLVM IR are query-fied. That is, lexing, parsing, name resolution, and macro
 expansion are done all at once for the whole program.