Fix build error on Python 3.9 for Windows
Created by: cgohlke
Fixes
_icu.cpp(209): error C2017: illegal escape sequence
_icu.cpp(209): error C2001: newline in constant
_icu.cpp(210): error C2146: syntax error: missing ')' before identifier 'PyObject_SetAttrString'
_icu.cpp(210): error C2146: syntax error: missing ';' before identifier 'PyObject_SetAttrString'
_icu.cpp(212): error C2017: illegal escape sequence
_icu.cpp(212): error C2001: newline in constant
_icu.cpp(213): error C2146: syntax error: missing ')' before identifier 'PyObject_SetAttrString'
_icu.cpp(213): error C2146: syntax error: missing ';' before identifier 'PyObject_SetAttrString'