[NFC] [lldb] Remove unused declaration

  /// section index 0 is never valid).

  lldb::user_id_t GetSectionIndexByName(const char *name);

  // Returns the ID of the first section that has the given type.

  lldb::user_id_t GetSectionIndexByType(unsigned type);

  /// Returns the section header with the given id or NULL.

  const ELFSectionHeaderInfo *GetSectionHeaderByIndex(lldb::user_id_t id);