[clang-format] Don't format typename template parameters as expression

bb4f6c4d made it so that template
parameter defaults are seen akin to assignments and formatted as
expressions, however, the patch did this for all template parameters,
even for `typename` template parameters.

This patch formats `typename` and `class` template parameters as types.

Fixes https://github.com/llvm/llvm-project/issues/61841

Reviewed By: HazardyKnusperkeks, owenpan, MyDeveloperDay

Differential Revision: https://reviews.llvm.org/D147318