Remove details blocks since Mermaid graphs don't display well inside

Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/development/pipelines.md

@@ -21,8 +21,6 @@ have a pipelines that include jobs from multiple types (e.g. a combination of do
 
 #### Docs-only MR pipeline
 
-<details><summary>Click to view the graph</summary>
-
 Reference pipeline: <https://gitlab.com/gitlab-org/gitlab/pipelines/135236627>
 
 ```mermaid
@@ -35,12 +33,8 @@ graph LR
   end
 ```
 
-</details>
-
 #### Code-only MR pipeline
 
-<details><summary>Click to view the graph</summary>
-
 Reference pipeline: <https://gitlab.com/gitlab-org/gitlab/pipelines/136295694>
 
 ```mermaid
@@ -152,12 +146,8 @@ graph RL;
   end
 ```
 
-</details>
-
 #### Frontend-only MR pipeline
 
-<details><summary>Click to view the graph</summary>
-
 Reference pipeline: <https://gitlab.com/gitlab-org/gitlab/pipelines/134661039>
 
 ```mermaid
@@ -296,12 +286,8 @@ graph RL;
   end
 ```
 
-</details>
-
 #### QA-only MR pipeline
 
-<details><summary>Click to view the graph</summary>
-
 Reference pipeline: <https://gitlab.com/gitlab-org/gitlab/pipelines/134645109>
 
 ```mermaid
@@ -359,8 +345,6 @@ graph RL;
   end
 ```
 
-</details>
-
 ### `workflow:rules`
 
 We're using the [`workflow:rules` keyword](../ci/yaml/README.md#workflowrules) to