fix(prompt-engineering): remove dead multimodal reference link (v1.1.1)

Co-Authored-By: duyetbot <duyetbot@users.noreply.github.com>

Author: duyet

prompt-engineering/.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "prompt-engineering",
-  "version": "1.1.0",
+  "version": "1.1.1",
   "description": "Prompt engineering skills for Grok, Claude, and Gemini LLMs with model-specific guidance and universal techniques",
   "author": { "name": "duyetbot" }
 }

prompt-engineering/.codex-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "prompt-engineering",
-  "version": "1.1.0",
+  "version": "1.1.1",
   "description": "Prompt engineering skills for Grok, Claude, and Gemini LLMs with model-specific guidance and universal techniques",
   "author": {
     "name": "duyetbot"

prompt-engineering/skills/prompt-engineering/SKILL.md

@@ -377,7 +377,6 @@ What's the latest on [topic] according to posts on X? Give me a summary of the c
 - `references/claude.md` - Claude-specific XML patterns
 - `references/gemini.md` - Gemini system instruction patterns
 - `references/grok.md` - Grok conversational patterns
-- `references/multimodal.md` - Multimodal prompting guide
 - `references/examples.md` - Concrete examples and templates
 
 ### Related Skills