Revert "build: package_type is dynamically set in conanfile.py depending if we build modules or not"

This reverts commit bbdb750362.

conanfile.py

@@ -82,6 +82,7 @@ class MPUnitsConan(ConanFile):
         "example/*",
         "CMakeLists.txt",
     )
+    package_type = "header-library"
     no_copy_source = True
 
     @property
@@ -203,10 +204,6 @@ class MPUnitsConan(ConanFile):
             self._set_default_option(key)
 
     def configure(self):
-        if self.options.cxx_modules:
-            self.package_type = "static-library"
-        else:
-            self.package_type = "header-library"
         if self.options.freestanding:
             self.options.rm_safe("std_format")