CMakePackageConfigHelpers: Fix note about version files supporting ranges

In commit 55c3b6a77e (CMakePackageConfigHelpers: Relax restrictions on
version range, 2019-05-30, v3.20.0-rc1~295^2~1) the documentation for
write_basic_package_version_file documented the support of version
ranges by the generated version files, however the note wrongly
specifies a COMPATIBILITY_MODE argument, instead of COMPATIBILITY.

Modules/CMakePackageConfigHelpers.cmake

@@ -177,9 +177,9 @@ macro.
   packages with no binaries.
 
 .. versionadded:: 3.19
-  ``COMPATIBILITY_MODE`` ``AnyNewerVersion``, ``SameMajorVersion`` and
-  ``SameMinorVersion`` handle the version range if any is specified
-  (see :command:`find_package` command for the details).
+  The version file generated by ``AnyNewerVersion``, ``SameMajorVersion`` and
+  ``SameMinorVersion`` arguments of ``COMPATIBILITY`` handle the version range
+  if any is specified (see :command:`find_package` command for the details).
   ``ExactVersion`` mode is incompatible with version ranges and will display an
   author warning if one is specified.