docs: kvm: x86: Fix broken field list

Add a missing ":" to fix a broken field list.
Signed-off-by: Takahiro Itazuri <itazur@amazon.com>
Fixes: ba7bb663 ("KVM: x86: Provide per VM capability for disabling PMU virtualization")
Message-Id: <20230331093116.99820-1-itazur@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virt/kvm/api.rst

@@ -8296,11 +8296,11 @@ ENOSYS for the others.
 8.35 KVM_CAP_PMU_CAPABILITY
 ---------------------------
 
-:Capability KVM_CAP_PMU_CAPABILITY
+:Capability: KVM_CAP_PMU_CAPABILITY
 :Architectures: x86
 :Type: vm
 :Parameters: arg[0] is bitmask of PMU virtualization capabilities.
-:Returns 0 on success, -EINVAL when arg[0] contains invalid bits
+:Returns: 0 on success, -EINVAL when arg[0] contains invalid bits
 
 This capability alters PMU virtualization in KVM.