ICU-22194 runConfigureICU computer->compiler

@josephshen found that the help text here has the wrong word, and I dropped the ball on his PR #2217 :-(

icu4c/source/runConfigureICU

diff --git a/icu4c/source/runConfigureICU b/icu4c/source/runConfigureICU
index 3f8576d..00a5687 100755
--- a/icu4c/source/runConfigureICU
+++ b/icu4c/source/runConfigureICU
@@ -54,7 +54,7 @@
     MacOSX              Use the default compilers on MacOS X (Darwin)
     MacOSX/GCC          Use the GNU gcc/g++ compilers on MacOSX (Darwin)
     MinGW               Use the GNU gcc/g++ compilers on MinGW
-    MSYS/MSVC           Use the Microsoft Visual C++ computer on MSYS
+    MSYS/MSVC           Use the Microsoft Visual C++ compiler on MSYS
     QNX                 Use the QNX QCC compiler on QNX/Neutrino
     Solaris             Use the Sun cc/CC compilers on Solaris
     Solaris/GCC         Use the GNU gcc/g++ compilers on Solaris