Fix reflection.fbs import path (#8499)

We need to copy the .fbs files into the package used for .bfbs files.
This is necessary as flatc doesn't provide support to specify the full
output file name for an .fbs file in a different folder.
I tried OUTPUT_FILE env var but this doesn't seem to be honored by
flatc.

reflection/ts/BUILD.bazel

@@ -1,15 +1,8 @@
 load("//:typescript.bzl", "flatbuffer_ts_library")
 
-genrule(
-    name = "copy_schema_to_folder",
-    srcs = ["//reflection:reflection_fbs_schema"],
-    outs = ["reflection.fbs"],
-    cmd = "cp $< $@",
-)
-
 flatbuffer_ts_library(
     name = "reflection_ts_fbs",
-    srcs = [":reflection.fbs"],
+    srcs = ["//reflection:reflection.fbs"],
     gen_reflections = True,
     visibility = ["//visibility:public"],
 )