ceph.spec.in: use gcc-toolset-10 for building crimson

ceph.spec.in: use gcc-toolset-10 for building crimson

This commit bumps up the toolset version but only to build crimson.
That is, the classical OSD stays unaffected.

The reason behind the upgrade is the following FTBFS:

```
[ 32%] Building CXX object src/seastar/CMakeFiles/seastar.dir/src/core/reactor.cc.o
/home/jenkins-build/build/workspace/ceph-dev-build/ARCH/x86_64/AVAILABLE_ARCH/x86_64/AVAILABLE_DIST/centos8/DIST/centos8/MACHINE_SIZE/gigantic/release/17.0.0-11345-ga3bb1485/rpm/el8/BUILD/ceph-17.0.0-11345-ga3bb1485/src/seastar/src/core/reactor.cc: In constructor ‘seastar::reactor::reactor(std::shared_ptr<seastar::smp>, seastar::alien::instance&, unsigned int, seastar::reactor_backend_selector, seastar::reactor_config)’:
/home/jenkins-build/build/workspace/ceph-dev-build/ARCH/x86_64/AVAILABLE_ARCH/x86_64/AVAILABLE_DIST/centos8/DIST/centos8/MACHINE_SIZE/gigantic/release/17.0.0-11345-ga3bb1485/rpm/el8/BUILD/ceph-17.0.0-11345-ga3bb1485/src/seastar/src/core/reactor.cc:926:90: error: use of deleted function ‘seastar::condition_variable::condition_variable()’
  926 |     , _thread_pool(std::make_unique<thread_pool>(this, seastar::format("syscall-{}", id))) {
      |                                                                                          ^
In file included from /home/jenkins-build/build/workspace/ceph-dev-build/ARCH/x86_64/AVAILABLE_ARCH/x86_64/AVAILABLE_DIST/centos8/DIST/centos8/MACHINE_SIZE/gigantic/release/17.0.0-11345-ga3bb1485/rpm/el8/BUILD/ceph-17.0.0-11345-ga3bb1485/src/seastar/include/seastar/core/reactor.hh:74,
                 from /home/jenkins-build/build/workspace/ceph-dev-build/ARCH/x86_64/AVAILABLE_ARCH/x86_64/AVAILABLE_DIST/centos8/DIST/centos8/MACHINE_SIZE/gigantic/release/17.0.0-11345-ga3bb1485/rpm/el8/BUILD/ceph-17.0.0-11345-ga3bb1485/src/seastar/src/core/reactor.cc:32:
/home/jenkins-build/build/workspace/ceph-dev-build/ARCH/x86_64/AVAILABLE_ARCH/x86_64/AVAILABLE_DIST/centos8/DIST/centos8/MACHINE_SIZE/gigantic/release/17.0.0-11345-ga3bb1485/rpm/el8/BUILD/ceph-17.0.0-11345-ga3bb1485/src/seastar/include/seastar/core/condition-variable.hh:157:5: note: ‘seastar::condition_variable::condition_variable() noexcept’ is implicitly deleted because its exception-specification does not match the implicit exception-specification ‘’
  157 |     condition_variable() noexcept = default;
```

Signed-off-by: Radosław Zarzyński <rzarzyns@redhat.com>