Add missing get_data when calling CFStringCreateWithCString in macos_utils

[a-johnston]

Related to #101293

Noticed local builds failing with scons module_mono_enabled=yes dev_mode=yes dev_build=yes (but not scons dev_mode=yes dev_build=yes for some reason) after rebasing earlier today and bisected to the above pr. I assume this instance was missed as it's behind MACOS_ENABLED. The build error is:

[ 56%] modules/mono/utils/macos_utils.cpp:41:26: error: no matching function for call to 'CFStringCreateWithCString'
   41 |         CFStringRef bundle_id = CFStringCreateWithCString(nullptr, p_bundle_id.utf8(), kCFStringEncodingUTF8);
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.1.sdk/System/Library/Frameworks/CoreFoundation.framework/Headers/CFString.h:181:13: note: candidate function not viable: no known conversion from 'CharString' to 'const char *' for 2nd argument
  181 | CFStringRef CFStringCreateWithCString(CFAllocatorRef alloc, const char *cStr, CFStringEncoding encoding) CF_FORMAT_ARGUMENT(2);
      |             ^                                               ~~~~~~~~~~~~~~~~