tools: fix broken link in icu notes

Link text and url were swapped around, this pr puts
the link text inside [] and the url inside ().

PR-URL: nodejs#20030
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

tools/icu/README.md

@@ -1,7 +1,7 @@
 # Notes about the `tools/icu` subdirectory
 
 This directory contains tools, data, and information about the
-[http://icu-project.org](ICU) (International Components for Unicode)
+[ICU](http://icu-project.org) (International Components for Unicode)
 integration. ICU is used to provide internationalization functionality.
 
 - `patches/` are one-off patches, actually entire source file replacements,