[SymForce] Remove unnecessary tl::optional alias

tl::optional now does this correctly in version 1.1.0, and new cmake
policies complain if we define it again:
TartanLlama/optional@54f7f97

Topic: tl-optional-no-alias
Reviewers: bradley,nathan,chao,hayk
GitOrigin-RevId: 43e352396cf411b68aacbd98fa14e53e7d6543ab

symforce/opt/CMakeLists.txt

@@ -68,9 +68,6 @@ if (NOT tl_optional_FOUND)
       URL_HASH SHA256=a336bb10f51945369c1dd6dc6d2a7086602ab9cab52c98a7a6224bfd782bc0c7
     )
     FetchContent_MakeAvailable(tl_optional)
-
-    # tl::optional does this correctly for installs, but not direct includes with FetchContent
-    add_library(tl::optional ALIAS optional)
   endfunction()
 
   add_tl_optional()