doc: update example ICU URL

PR-URL: #35373
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/guides/maintaining-icu.md

@@ -83,7 +83,7 @@ V8 will not compile.
 
 ```c
 // deps/v8/src/objects/intl-objects.h
-#define V8_MINIMUM_ICU_VERSION 64
+#define V8_MINIMUM_ICU_VERSION 65
 ```
 
 V8 in Node.js depends on the ICU version supplied by Node.js.
@@ -104,7 +104,7 @@ should be sufficient).
 ```bash
 ./configure \
     --with-intl=full-icu \
-    --with-icu-source=http://download.icu-project.org/files/icu4c/58.1/icu4c-58_1-src.tgz
+    --with-icu-source=https://github.com/unicode-org/icu/releases/download/release-67-1/icu4c-67_1-src.tgz
 make
 ```