Revert: "Change: Allow AI companies to start immediately."

This reverts commit 011257dc88.

This commit was not working properly. Attempts are made to fix it,
but so close to 1.9, it sounds a lot better to revert it from the
1.9 branch, and keep developing it further in 1.10.

src/ai/ai_config.cpp

@@ -127,14 +127,3 @@ void AIConfig::SetSetting(const char *name, int value)
 
 	ScriptConfig::SetSetting(name, value);
 }
-
-void AIConfig::AddRandomDeviation()
-{
-	int start_date = this->GetSetting("start_date");
-
-	ScriptConfig::AddRandomDeviation();
-
-	/* start_date = 0 is a special case, where random deviation does not occur.
-	 * If start_date was not already 0, then a minimum value of 1 must apply. */
-	this->SetSetting("start_date", start_date != 0 ? max(1, this->GetSetting("start_date")) : 0);
-}