Fix link to Gridcoin.ico in Makefile.am
Fix link to Gridcoin.ico in Makefile.am

Fixes trivial Travis compile error.

Git-Jiro/Gridcoin-Research,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,theMarix/Gridcoin-Research,gridcoin/Gridcoin-Research,theMarix/Gridcoin-Research,Git-Jiro/Gridcoin-Research,gridcoin/Gridcoin-Research,gridcoin/Gridcoin-Research,gridcoin/Gridcoin-Research,gridcoin/Gridcoin-Research,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,theMarix/Gridcoin-Research,caraka/gridcoinresearch,caraka/gridcoinresearch,theMarix/Gridcoin-Research,caraka/gridcoinresearch,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,theMarix/Gridcoin-Research,theMarix/Gridcoin-Research,gridcoin/Gridcoin-Research