[mlir][vscode] Don't inject inside strings

Avoids matching R"mlir( while already inside a string.

mlir/utils/vscode/cpp-grammar.json

@@ -1,6 +1,6 @@
 {
   "scopeName": "source.cpp.mlir",
-  "injectionSelector": "L:source.cpp",
+  "injectionSelector": "L:source.cpp -string.quoted.double.cpp -string.quoted.double.raw",
   "patterns": [
     {
       "include": "#mlir-raw-string"

mlir/utils/vscode/package.json

@@ -2,7 +2,7 @@
   "name": "vscode-mlir",
   "displayName": "MLIR",
   "description": "MLIR Language Extension",
-  "version": "0.0.3",
+  "version": "0.0.4",
   "publisher": "llvm-vs-code-extensions",
   "homepage": "https://mlir.llvm.org/",
   "icon": "icon.png",