Increase timeout in test that takes a bit longer on riscv64

[SnarkBoojum]

Stéphane Glondu noticed a failure for the Debian coq-elpi package on the riscv64 architecture, and added this patch to get around it:

diff --git a/tests/test_API_env.v b/tests/test_API_env.v
index 341b55f..5a37537 100644
--- a/tests/test_API_env.v
+++ b/tests/test_API_env.v
@@ -340,7 +340,7 @@ Elpi Query lp:{{
   coq.locate "Ranalysis5.derivable_pt_lim_CVU" GR,
   std.time (coq.env.transitive-dependencies GR _ S) T,
   std.assert! ({coq.gref.set.cardinal S} > 3000) "too few",
-  std.assert! (T < 10.0) "too slow" % 0.5 here
+  std.assert! (T < 20.0) "too slow" % 0.5 here
 
 }}.