Remove references in the website to unsupported distributions
Remove references in the website to unsupported distributions

All the AT releases supporting Fedora 19, Red Hat 6 and Ubuntu 14.10
reached EOL.

Signed-off-by: Tulio Magno Quites Machado Filho <0e1b3d0765ee75ed64fa2e34822e4949a70a1429@linux.ibm.com>

advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain,advancetoolchain/advance-toolchain