golang: increase timeout for webp decoding target (#13426)

We see a not insignificant number of timeout issues when running the
fuzz_webp_decode target, which appear to magically resolve themselves
despite the underlying code not changing.

I expect that running the target under ASAN, with limited resources, is
just a little slow.

Bump the timeout from the default (60s) to 120s. I expect this will just
silence the timeouts.

Author: rolandshoemaker

projects/golang/fuzz_webp_decode.options

@@ -0,0 +1,2 @@
+[libfuzzer]
+timeout = 120