tools.go,vendor: Remove trailing slash in github.com/go-bindata/go-bindata module

Update the tools.go and remove the trailing slash in the
`github.com/go-bindata/go-bindata/v3/go-bindata` module.

When attempting to run `make vendor` from the root repository, the
following error is produced:

```bash
$ make vendor
go mod tidy
warning: ignoring symlink /home/tflannag/go/src/github.com/operator-framework/operator-lifecycle-manager/deploy/ocp/manifests/latest
warning: ignoring symlink /home/tflannag/go/src/github.com/operator-framework/operator-lifecycle-manager/deploy/upstream/manifests/latest
github.com/operator-framework/operator-lifecycle-manager imports
	github.com/go-bindata/go-bindata/v3/go-bindata/: malformed import path "github.com/go-bindata/go-bindata/v3/go-bindata/": trailing slash
make: *** [Makefile:176: vendor] Error 1
```

After after removing the trailing slash, updating the vendor tree was
successful:

```diff
$ git diff tools.go
diff --git a/tools.go b/tools.go
index 387556b..949acdc 100644
--- a/tools.go
+++ b/tools.go
@@ -3,7 +3,7 @@
 package tools

 import (
-       _ "github.com/go-bindata/go-bindata/v3/go-bindata/"
+       _ "github.com/go-bindata/go-bindata/v3/go-bindata"
        _ "github.com/golang/mock/mockgen"
        _ "github.com/googleapis/gnostic"
        _ "github.com/maxbrunsfeld/counterfeiter/v6"
```
```bash
$ make vendor
go mod tidy
warning: ignoring symlink /home/tflannag/go/src/github.com/operator-framework/operator-lifecycle-manager/deploy/ocp/manifests/latest
warning: ignoring symlink /home/tflannag/go/src/github.com/operator-framework/operator-lifecycle-manager/deploy/upstream/manifests/latest
go mod vendor
warning: ignoring symlink /home/tflannag/go/src/github.com/operator-framework/operator-lifecycle-manager/deploy/ocp/manifests/latest
warning: ignoring symlink /home/tflannag/go/src/github.com/operator-framework/operator-lifecycle-manager/deploy/upstream/manifests/latest
```

Signed-off-by: timflannagan <[email protected]>

Author: timflannagan

tools.go

@@ -3,7 +3,7 @@
 package tools
 
 import (
-	_ "github.com/go-bindata/go-bindata/v3/go-bindata/"
+	_ "github.com/go-bindata/go-bindata/v3/go-bindata"
 	_ "github.com/golang/mock/mockgen"
 	_ "github.com/googleapis/gnostic"
 	_ "github.com/maxbrunsfeld/counterfeiter/v6"

vendor/modules.txt

@@ -204,7 +204,7 @@ github.com/ghodss/yaml
 # github.com/go-bindata/go-bindata/v3 v3.1.3
 ## explicit
 github.com/go-bindata/go-bindata/v3
-github.com/go-bindata/go-bindata/v3/go-bindata/
+github.com/go-bindata/go-bindata/v3/go-bindata
 # github.com/go-logr/logr v0.3.0
 ## explicit
 github.com/go-logr/logr