Context:

Our CMake support scripts have copyright notice headers. These however don't get correspondingly checked by our dist/s_copyright script.

On a closer inspection, our dist scripts never performed copyright checks on our autoconf build support files since its something we don't generally need to worry about.  Similar to autoconf, we should also remove the headers in CMake as to generally simplify management of sources with license headers in WiredTiger.

Definition of Done:

Remove license headers from any cmake support scripts e.g. CMakeLists.txt, .cmake.