build(deps): bump node from 22-slim to 26-slim in /services/socket-mode

Bumps node from 22-slim to 26-slim.

---
updated-dependencies:
- dependency-name: node
  dependency-version: 26-slim
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

services/socket-mode/Dockerfile

@@ -1,11 +1,11 @@
-FROM node:22-slim AS builder
+FROM node:26-slim AS builder
 WORKDIR /app
 COPY package*.json tsconfig.json ./
 RUN npm ci
 COPY src/ src/
 RUN npx tsc
 
-FROM node:22-slim
+FROM node:26-slim
 WORKDIR /app
 COPY --from=builder /app/dist ./dist
 COPY --from=builder /app/node_modules ./node_modules