Update header style in release notes template (#1281)

Signed-off-by: Brentley Jones <[email protected]>

Author: brentleyjones

.github/generate-notes.sh

@@ -14,13 +14,13 @@ TODO
 
 This release is compatible with: TODO
 
-### MODULE.bazel Snippet
+## MODULE.bazel Snippet
 
 \`\`\`bzl
 bazel_dep(name = "rules_swift", version = "$new_version", repo_name = "build_bazel_rules_swift")
 \`\`\`
 
-### Workspace Snippet
+## Workspace Snippet
 
 \`\`\`bzl
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")