Use npm in grammar:build

`pnpm` is not available in that job.

.github/workflows/ci-backend.yml

@@ -145,7 +145,7 @@ jobs:
                   cd current
                   npm run schema:build:python && git diff --exit-code
 
-            - name: Check if antlr definitions are up to date
+            - name: Check if ANTLR definitions are up to date
               run: |
                   # Installing a version of ant compatible with what we use in development from homebrew (4.13)
                   # "apt-get install antlr" would install 4.7 which is incompatible with our grammar.

package.json

@@ -39,7 +39,7 @@
         "schema:build": "pnpm run schema:build:json && pnpm run schema:build:python",
         "schema:build:json": "ts-json-schema-generator -f tsconfig.json --path 'frontend/src/*.ts' --type 'QuerySchema' --no-type-check > frontend/src/queries/schema.json && prettier --write frontend/src/queries/schema.json",
         "schema:build:python": "datamodel-codegen --collapse-root-models --disable-timestamp --use-one-literal-as-default --use-default-kwarg --use-subclass-enum --input frontend/src/queries/schema.json --input-file-type jsonschema --output posthog/schema.py --output-model-type pydantic_v2.BaseModel && black posthog/schema.py",
-        "grammar:build": "pnpm grammar:build:python && pnpm grammar:build:cpp",
+        "grammar:build": "npm run grammar:build:python && npm run grammar:build:cpp",
         "grammar:build:python": "cd posthog/hogql/grammar && antlr -Dlanguage=Python3 HogQLLexer.g4 && antlr -visitor -no-listener -Dlanguage=Python3 HogQLParser.g4",
         "grammar:build:cpp": "cd posthog/hogql/grammar && antlr -o ../../../hogql_parser -Dlanguage=Cpp HogQLLexer.g4 && antlr -o ../../../hogql_parser -visitor -no-listener -Dlanguage=Cpp HogQLParser.g4",
         "packages:build": "pnpm packages:build:apps-common && pnpm packages:build:lemon-ui",