Adapt expected error string in stack-snapshot-deps test

Before, it expected "parsing JSON failed", but the json.decode function returns
a different error:
```
Error in decode: at offset 5, invalid number: 2.3.1
```

Author: avdv

rules_haskell_tests/tests/stack-snapshot-deps/HsOverrideStackTest.hs

@@ -2,12 +2,14 @@
 
 import Data.List (isInfixOf)
 import IntegrationTesting
-import Test.Hspec (hspec, it)
+import Test.Hspec (describe, hspec, it)
 
 main :: IO ()
 main =  hspec $ do
-  it "bazel run repl" $ do
-    bazel <- setupTestBazel
-    let p (_stdout, stderr) = "parsing JSON failed" `isInfixOf` stderr
-     in
-       failedOutputSatisfy p (bazel ["run", "//:hs-bin@repl", "--", "-ignore-dot-ghci", "-e", ":main"])
+  describe "bazel run repl" $ do
+    it "fails with a json decode error" $ do
+      -- this is evidence that it used the deficient `stack` script provided in hs_override_stack_test/
+      bazel <- setupTestBazel
+      let p (_stdout, stderr) = "Error in decode: at offset" `isInfixOf` stderr
+       in
+         failedOutputSatisfy p (bazel ["run", "//:hs-bin@repl", "--", "-ignore-dot-ghci", "-e", ":main"])