Removing check for leading hyphens in .NET FirefoxOptions AddArgument

In prior releases of geckodriver, it was a requirement that all arguments be preceeded by double hyphens ("--"). Geckodriver has now relaxed that restriction, and the .NET bindings need to keep up with that change. This commit removes the check for leading hyphens when calling AddArgument.

Author: jimevans

dotnet/src/webdriver/Firefox/FirefoxOptions.cs

@@ -76,10 +76,6 @@ public FirefoxOptions()
  : base()
  {
  this.BrowserName = BrowserNameValue;
- /*capabilityName == IsMarionetteCapability ||
- capabilityName == FirefoxLegacyProfileCapability ||
- capabilityName == FirefoxLegacyBinaryCapability ||
- capabilityName == FirefoxOptionsCapability)*/
  this.AddKnownCapabilityName(FirefoxOptions.FirefoxOptionsCapability, "current FirefoxOptions class instance");
  this.AddKnownCapabilityName(FirefoxOptions.IsMarionetteCapability, "UseLegacyImplementation property");
  this.AddKnownCapabilityName(FirefoxOptions.FirefoxProfileCapability, "Profile property");
@@ -183,14 +179,6 @@ public void AddArguments(IEnumerable<string> argumentsToAdd)
  throw new ArgumentNullException("argumentsToAdd", "argumentsToAdd must not be null");
  }
 
- foreach (string argument in argumentsToAdd)
- {
- if (!argument.StartsWith("--", StringComparison.OrdinalIgnoreCase))
- {
- throw new ArgumentException(string.Format(CultureInfo.InvariantCulture, "All arguments must start with two dashes ('--'); argument '{0}' does not.", argument), "argumentsToAdd");
- }
- }
-
  this.firefoxArguments.AddRange(argumentsToAdd);
  }