Update texture_srgb.html (WebGLSamples#161)

Fixed typo.

Author: spite

Diff for: samples/texture_srgb.html

@@ -17,7 +17,7 @@
         <br>
         This is useful since because then we could work with the filtering math in linear space, then convert back to sRGB space for the color output.
         <br>
-        The output below is applied to a Guassian blur filter.
+        The output below is applied to a Gaussian blur filter.
 
     </p>
     <!-- Shader code is modified adapted from xissburg at http://xissburg.com/faster-gaussian-blur-in-glsl/ -->