[TS] Fix getFullyQualifiedName codegen for typescript (#7730)

#7451 caused getFullyQualifiedName to return a name with underscores,
not periods. Because the fully qualified name is a property of
FlatBuffers, not the language being codegen'd for, it should use
periods. Fixes #7564.

Co-authored-by: Derek Bailey <derekbailey@google.com>

tests/ts/reflection/enum.js

@@ -69,7 +69,7 @@ export class Enum {
         return offset ? this.bb.__string(this.bb_pos + offset, optionalEncoding) : null;
     }
     static getFullyQualifiedName() {
-        return 'reflection_Enum';
+        return 'reflection.Enum';
     }
     static startEnum(builder) {
         builder.startObject(7);