rescaler_mips32: disable ImportRowShrink

this function is failing the 'accum == 0' assert on skia bots for
rescaling to 13x13

BUG=skia:6682

Change-Id: I9f9f3adf28cec63ad6e38ed3128f18825d5b70cc

src/dsp/rescaler_mips32.c

@@ -279,7 +279,8 @@ extern void WebPRescalerDspInitMIPS32(void);
 
 WEBP_TSAN_IGNORE_FUNCTION void WebPRescalerDspInitMIPS32(void) {
   WebPRescalerImportRowExpand = ImportRowExpand;
-  WebPRescalerImportRowShrink = ImportRowShrink;
+  // WebPRescalerImportRowShrink = ImportRowShrink;
+  (void)ImportRowShrink;
   WebPRescalerExportRowExpand = ExportRowExpand;
   WebPRescalerExportRowShrink = ExportRowShrink;
 }