boost: fixed syntax error

[eigenwhat]

Specify library name and version: boost/1.74.0

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[ghost]

I detected other pull requests that are modifying boost recipe:

• Boost: Change assertions to warnings #3900
• [boost] Add nowide lib #3894
• boost: add boost/1.75.0 #3872
• Add --disable-icu flag for iconv backend #3855
• Fix boost syntax warning #3522
• boost: no quotes around compiler (os.environ["CXX"]) #3362
• Link boost coroutine_exe against CONAN_LIBS #3205
• Boost/1.72.0 : enabling mpi #2842
• boost: Correct --disable-iconv option #2657
• Boost components #1925
• boost: fix i18n_backend=icu support for version 1.7{1,2,3}.0 #1704

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[conan-center-bot]

An unexpected error happened and has been reported. Help is on its way! 🏇

[conan-center-bot]

All green in build 4 (529bde1efcd9c7a0976c40f8cf511e0278e8ca3e)! 😊

• boost/1.69.0: Generated 131 packages. All logs here
• boost/1.70.0: Generated 131 packages. All logs here
• boost/1.71.0: Generated 131 packages. All logs here
• boost/1.72.0: Generated 131 packages. All logs here
• boost/1.73.0: Generated 131 packages. All logs here
• boost/1.74.0: Generated 131 packages. All logs here

[conan-center-bot]

All green in build 5 (529bde1efcd9c7a0976c40f8cf511e0278e8ca3e)! 😊

• boost/1.69.0: Generated 131 packages. All logs here
• boost/1.70.0: Generated 131 packages. All logs here
• boost/1.71.0: Generated 131 packages. All logs here
• boost/1.72.0: Generated 131 packages. All logs here
• boost/1.73.0: Generated 131 packages. All logs here
• boost/1.74.0: Generated 131 packages. All logs here