chore: bump version to 18.2.0-rc.4 (#5117)

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configure.ac

@@ -2,7 +2,7 @@ AC_PREREQ([2.69])
 define(_CLIENT_VERSION_MAJOR, 18)
 define(_CLIENT_VERSION_MINOR, 2)
 define(_CLIENT_VERSION_BUILD, 0)
-define(_CLIENT_VERSION_RC, 3)
+define(_CLIENT_VERSION_RC, 4)
 define(_CLIENT_VERSION_IS_RELEASE, false)
 define(_COPYRIGHT_YEAR, 2022)
 define(_COPYRIGHT_HOLDERS,[The %s developers])