We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg→H→W+W− in pp collisions at the Fermilab Tevatron Collider at s√=1.96  TeV. With 4.8  fb−1 of integrated luminosity analyzed at CDF and 5.4  fb−1 at D0, the 95% confidence level upper limit on σ(gg→H)×B(H→W+W−) is 1.75 pb at mH=120  GeV, 0.38 pb at mH=165  GeV, and 0.83 pb at mH=200  GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.