move texture files from foundation -> stdassets

Author: davidkline-ms

…rdAssets/Textures/IridescentSpectrum.png …rdAssets/Textures/IridescentSpectrum.pngAssets/MRTK/SDK/StandardAssets/Textures/IridescentSpectrum.png renamed to Assets/MRTK/StandardAssets/Textures/IridescentSpectrum.png Assets/MRTK/SDK/StandardAssets/Textures/IridescentSpectrum.png renamed to Assets/MRTK/StandardAssets/Textures/IridescentSpectrum.png

@@ -27,7 +27,6 @@
         "url": "https://github.com/microsoft/MixedRealityToolkit-Unity/issues"
     },
     "dependencies": {
-        "com.thirdparty.mrtk.foundation": "2.5.0",
         "com.unity.textmeshpro": "2.1.1"
     }
 }