Remove mentions that SPDX 3 is not released yet Signed-off-by: Arthit Suriyawongkul <[email protected]>

spdx-tools v0.8.3 

spdx-tools v0.8.2 

spdx-tools v0.8.1 

spdx-tools v0.8.0 

spdx-tools v0.8.0rc3 

python spdx tools v0.8.0rc2 

python spdx tools v0.8.0rc1 

python spdx tools v0.8.0a3 

First 0.8.0 alpha tag