Make U-1700 speculative instead of altHist (#3006)

It literally says it is "speculative" twice in the description. The U-1700 is about as unreal as some other engines labeled "speculative," such as the later variants of E-1 and HG-3.

GameData/RealismOverhaul/Engine_Configs/U1250_Config.cfg

@@ -151,7 +151,7 @@
 		{
 			name = U-1700
 			description = Speculative upgrade for the U-1250
-			specLevel = altHist
+			specLevel = speculative
 			maxThrust = 19.411
 			minThrust = 19.411
 			massMult = 1.0