Remove substance material due to support being removed in Unity

MaterialGraphProject/Assets/TestAssets/RockMaterial1.sbsar.meta

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-timeCreated: 1495753980
-licenseType: Pro
-SubstanceImporter:
-  serializedVersion: 5
-  materialInstances:
-  - serializedVersion: 16
-    name: RockMaterial1
-    prototypeName: RockMaterial1
-    shaderName: 
-    shader: {fileID: 46, guid: 0000000000000000f000000000000000, type: 0}
-    shaderKeywords: 
-    renderQueue: -1
-    lightmapFlags: 4
-    inputs: []
-    materialInformation:
-      serializedVersion: 5
-      offset: {x: 0, y: 0}
-      scale: {x: 1, y: 1}
-      generateMipmaps: 1
-      generateAllOutputs: 0
-      animationUpdateRate: 0
-    materialProperties:
-      serializedVersion: 3
-      texEnvs: []
-      floats: []
-      colors: []
-    textureParameters:
-    - name: RockMaterial1_basecolor
-      alphaSource: 6
-      filterMode: 1
-      aniso: 1
-      wrapMode: 0
-    - name: RockMaterial1_normal
-      alphaSource: 0
-      filterMode: 1
-      aniso: 1
-      wrapMode: 0
-    - name: RockMaterial1_metallic
-      alphaSource: 7
-      filterMode: 1
-      aniso: 1
-      wrapMode: 0
-    textureAssignments:
-    - shaderProp: _MainTex
-      material: {instanceID: 0}
-      baseUID: 779270956
-    - shaderProp: _BumpMap
-      material: {instanceID: 0}
-      baseUID: 779270958
-    - shaderProp: _MetallicGlossMap
-      material: {instanceID: 0}
-      baseUID: 779270954
-    buildTargetSettings:
-    - serializedVersion: 2
-      buildTarget: 
-      textureWidth: 512
-      textureHeight: 512
-      textureFormat: 0
-      loadingBehavior: 1
-  deletedPrototypes: []
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