cmExperimental: Make CPS-export experimental notice more consistent

There is an inadvertent inconsistency in the notice for the CPS export
experimental feature as compared to other experimental feature notices.
Change it to be consistent.

Source/cmExperimental.cxx

@@ -51,8 +51,8 @@ cmExperimental::FeatureData LookupTable[] = {
     "b80be207-778e-46ba-8080-b23bba22639e",
     "CMAKE_EXPERIMENTAL_EXPORT_PACKAGE_INFO",
     "CMake's support for exporting package information in the Common Package "
-    "Specification format. It is meant only for experimentation and feedback "
-    "to CMake developers.",
+    "Specification format is experimental. It is meant only for "
+    "experimentation and feedback to CMake developers.",
     {},
     cmExperimental::TryCompileCondition::Always,
     false },

Tests/RunCMake/PackageInfo/ExperimentalWarning-stderr.txt

@@ -1,7 +1,7 @@
 CMake Warning \(dev\) at ExperimentalWarning.cmake:8 \(install\):
   CMake's support for exporting package information in the Common Package
-  Specification format.  It is meant only for experimentation and feedback to
-  CMake developers.
+  Specification format is experimental\.  It is meant only for experimentation
+  and feedback to CMake developers\.
 Call Stack \(most recent call first\):
   CMakeLists.txt:3 \(include\)
 This warning is for project developers.  Use -Wno-dev to suppress it.