No, 29xx ISRs do not support a performance upgrade via license (as do the later 4K ISRs).
BTW, the 75 Mbps recommendation, is just that, a recommendation. Generally, Cisco performance recommendations are very conservative insuring that you won't exceed CPU capacity if you keep within the recommendation. However, your "mileage may vary" and you often can drive more bandwidth than such a recommendation.
Since you mention 75 Mbps, I assume you saw that in the attached document? If so, take careful note of the how the 2951 performs under different situations, including being able to support up to 5 Gbps of bandwidth, in an ideal situation.
PS:
Also BTW, the 75 Mbps would be duplex (i.e. up to 150 Mbps to support ingress and egress, e.g. 100 Mbps down and 50 Mbps up, etc.), while the 5 Gbps is not.