rename legacy_icu tokenizer to icu tokenizer

The new icu tokenizer is now no longer compatible with the old
legacy tokenizer in terms of data structures. Therefore there
is also no longer a need to refer to the legacy tokenizer in the
name.

CMakeLists.txt

@@ -258,6 +258,6 @@ install(FILES settings/env.defaults
               settings/import-address.style
               settings/import-full.style
               settings/import-extratags.style
-              settings/legacy_icu_tokenizer.yaml
+              settings/icu_tokenizer.yaml
               settings/icu-rules/extended-unicode-to-asccii.yaml
         DESTINATION ${NOMINATIM_CONFIGDIR})