mesa: fix 'feeedback' typo in comment

Trivial.
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 051a85f..415d302 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2775,7 +2775,7 @@
     * Transform feedback varyings last specified by
     * glTransformFeedbackVaryings().
     *
-    * For the current set of transform feeedback varyings used for transform
+    * For the current set of transform feedback varyings used for transform
     * feedback output, see LinkedTransformFeedback.
     */
    struct {