meson: remove with_shared_glapi variable (it's always true)

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33794>

src/mapi/glapi/meson.build

@@ -67,7 +67,7 @@ libglapi_bridge = static_library(
   build_by_default : false,
 )
 
-if not with_shared_glapi
+if false
   libglapi_static = static_library(
     'glapi_static',
     static_glapi_files,

src/mapi/meson.build

@@ -147,8 +147,4 @@ glapi_xml_py_deps = files(
 )
 
 subdir('glapi')
-if with_shared_glapi
-  subdir('shared-glapi')
-else
-  libglapi = []
-endif
+subdir('shared-glapi')