Remove $Id$ markers since git doesn't support them

aegisub/automation/autoload/clean-info.lua

aegisub/automation/autoload/select-overlaps.lua

aegisub/automation/autoload/strip-tags.lua

aegisub/automation/include/clipboard.lua

aegisub/automation/include/re.lua

aegisub/libaegisub/Makefile

aegisub/libaegisub/common/charset.cpp

aegisub/libaegisub/common/charset_6937.cpp

aegisub/libaegisub/common/charset_6937.h

aegisub/libaegisub/common/charset_conv.cpp

aegisub/libaegisub/common/charset_ucd.cpp

aegisub/libaegisub/common/charset_ucd.h

aegisub/libaegisub/common/hotkey.cpp

aegisub/libaegisub/common/json.cpp

aegisub/libaegisub/common/keyframe.cpp

aegisub/libaegisub/common/log.cpp

aegisub/libaegisub/common/mru.cpp

aegisub/libaegisub/common/option.cpp

aegisub/libaegisub/common/option_visit.cpp

aegisub/libaegisub/common/option_visit.h