databases/evolution-data-server: unbreak with ICU 61

src/libedataserver/e-alphabet-index-private.cpp:79:2: error: unknown type name 'UnicodeString'; did you mean 'icu::UnicodeString'?

UnicodeString string;
^~~~~~~~~~~~~
icu::UnicodeString

/usr/local/include/unicode/unistr.h:286:20: note: 'icu::UnicodeString' declared here
class U_COMMON_API UnicodeString : public Replaceable

^

src/libedataserver/e-alphabet-index-private.cpp:132:3: error: unknown type name 'UnicodeString'; did you mean 'icu::UnicodeString'?

UnicodeString ustring;
^~~~~~~~~~~~~
icu::UnicodeString

/usr/local/include/unicode/unistr.h:286:20: note: 'icu::UnicodeString' declared here
class U_COMMON_API UnicodeString : public Replaceable

^

https://ssl.icu-project.org/trac/changeset/40705

PR: 227042
Reported by: antoine (via exp-run)