deps: Bump github.com/google/flatbuffers to v1.12.1 (#1746)

The v1.12.0 version of the flatbuffers package has an issue where the
hash of the package will differ depending on if you fetch the source
using the default, public Go Modules proxy or if you fetch the source
directly, which can cause build issues [1][2]. The flatbuffers maintainers
released v1.12.1 to fix this issue [3].

[1] https://github.com/open-policy-agent/conftest/runs/3576130950?check_suite_focus=true
[2] open-policy-agent/conftest#613
[3] google/flatbuffers#6466

Signed-off-by: James Alseth <james@jalseth.me>
(cherry picked from commit a6bf4fd)

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/gogo/protobuf v1.3.2
 	github.com/golang/protobuf v1.3.1
 	github.com/golang/snappy v0.0.3
-	github.com/google/flatbuffers v1.12.0
+	github.com/google/flatbuffers v1.12.1
 	github.com/google/go-cmp v0.5.4 // indirect
 	github.com/klauspost/compress v1.12.3
 	github.com/kr/pretty v0.1.0 // indirect

go.sum

@@ -34,8 +34,8 @@ github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/snappy v0.0.3 h1:fHPg5GQYlCeLIPB9BZqMVR5nR9A+IM5zcgeTdjMYmLA=
 github.com/golang/snappy v0.0.3/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
-github.com/google/flatbuffers v1.12.0 h1:/PtAHvnBY4Kqnx/xCQ3OIV9uYcSFGScBsWI3Oogeh6w=
-github.com/google/flatbuffers v1.12.0/go.mod h1:1AeVuKshWv4vARoZatz6mlQ0JxURH0Kv5+zNeJKJCa8=
+github.com/google/flatbuffers v1.12.1 h1:MVlul7pQNoDzWRLTw5imwYsl+usrS1TXG2H4jg6ImGw=
+github.com/google/flatbuffers v1.12.1/go.mod h1:1AeVuKshWv4vARoZatz6mlQ0JxURH0Kv5+zNeJKJCa8=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.5.4 h1:L8R9j+yAqZuZjsqh/z+F1NCffTKKLShY6zXTItVIZ8M=
 github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=