fix(tools/mongodb): concat filter params only once in mongodb update tools (#1545)

## Description

---
### What

Fixed a bug where `FilterParams` was being concatenated twice in the
parameter list for MongoDB update operations.

### Why

The duplicate concatenation would cause parameter validation to fail
during tool initialization, preventing the MongoDB update tools from
working.

### Changes

- `mongodbupdateone.go`: Fixed `slices.Concat()` to properly combine
FilterParams and UpdateParams
- `mongodbupdatemany.go`: Fixed `slices.Concat()` to properly combine
FilterParams and UpdateParams

## PR Checklist

---
> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:

- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
- [x] Make sure to add `!` if this involve a breaking change

internal/tools/mongodb/mongodbupdatemany/mongodbupdatemany.go

@@ -80,7 +80,7 @@ func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error)
 	}
 
 	// Create a slice for all parameters
-	allParameters := slices.Concat(cfg.FilterParams, cfg.FilterParams, cfg.UpdateParams)
+	allParameters := slices.Concat(cfg.FilterParams, cfg.UpdateParams)
 
 	// Verify no duplicate parameter names
 	err := tools.CheckDuplicateParameters(allParameters)

internal/tools/mongodb/mongodbupdateone/mongodbupdateone.go

@@ -81,7 +81,7 @@ func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error)
 	}
 
 	// Create a slice for all parameters
-	allParameters := slices.Concat(cfg.FilterParams, cfg.FilterParams, cfg.UpdateParams)
+	allParameters := slices.Concat(cfg.FilterParams, cfg.UpdateParams)
 
 	// Verify no duplicate parameter names
 	err := tools.CheckDuplicateParameters(allParameters)

tests/mongodb/mongodb_integration_test.go

@@ -666,8 +666,14 @@ func getMongoDBToolsConfig(sourceConfig map[string]any, toolKind string) map[str
 				"authRequired":  []string{},
 				"collection":    "test_collection",
 				"canonical":     true,
-				"filterPayload": `{ "id" : 300 }`,
-				"filterParams":  []any{},
+				"filterPayload": `{ "id" : {{ .id }} }`,
+				"filterParams": []map[string]any{
+					{
+						"name":        "id",
+						"type":        "integer",
+						"description": "id",
+					},
+				},
 				"updatePayload": `{ "$set" : { "name": {{json .name}} } }`,
 				"updateParams": []map[string]any{
 					{