fix: add missing library to build with libicu 76

Previously attempting to build with libicu 76 would result in
unresolved symbols:

```
Undefined symbols for architecture arm64:
  "_ucnv_close_76", referenced from:
      _convertToUtf16 in 000003.o
      _convertFromUtf16 in 000003.o
  "_ucnv_fromUChars_76", referenced from:
      _convertFromUtf16 in 000003.o
  "_ucnv_open_76", referenced from:
      _convertToUtf16 in 000003.o
      _convertFromUtf16 in 000003.o
  "_ucnv_toUChars_76", referenced from:
      _convertToUtf16 in 000003.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```

It appears that these symbols are now in the `icu-uc`. Update the icu
library in gitlab-org/go/icu!1 to
make this work. This should be backwards compatible with older libicu
versions.