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: #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

@@ -1,6 +1,6 @@
 # Notes about the `tools/icu` subdirectory
 
-This directory contains tools, data, and information about the [http://icu-project.org](ICU)
+This directory contains tools, data, and information about the [ICU](http://icu-project.org)
 (International Components for Unicode) integration. ICU is used to provide
 internationalization functionality.