Merge #12027: [Docs] Remove boost --c++ flag from osx build instructions

5ec3eae remove brew c++ flag (Pablo Fernandez)

Pull request description:

  the c++ is not needed since the listed brew formulas no longer have this option. It also raises a warning that may generate confusion.

Tree-SHA512: 37c0ebee2901947a21abfcd646ae0c7e73293568f37db9b130d1c521aa4222b0e82e21614e6ac60bb5347c34ef15bbd24eb8066ebf576ea3da9f365be9a4d062

doc/build-osx.md

@@ -16,7 +16,7 @@ Then install [Homebrew](https://brew.sh).
 Dependencies
 ----------------------
 
-    brew install automake berkeley-db4 libtool boost --c++11 miniupnpc openssl pkg-config protobuf python3 qt libevent
+    brew install automake berkeley-db4 libtool boost miniupnpc openssl pkg-config protobuf python3 qt libevent
 
 See [dependencies.md](dependencies.md) for a complete overview.