Rename `inst_eddies_in.py` to `inst_eddies.py.in`

Following convention for the source of `configure_file`. See Scott
2021 k1077, § 19.7.

Inst_eddies/CMakeLists.txt

@@ -15,6 +15,6 @@ target_link_libraries(inst_eddies PRIVATE Contour_531::contour_531
   Numer_Rec_95::numer_rec_95 NR_util::nr_util Jumble::jumble
   NetCDF_Fortran::netcdff)
 
-configure_file(inst_eddies_in.py inst_eddies.py @ONLY)
+configure_file(inst_eddies.py.in inst_eddies.py @ONLY)
 execute_process(COMMAND chmod -w ${CMAKE_CURRENT_BINARY_DIR}/inst_eddies.py)
 include(Tests/CMakeLists.txt)