ffi example: android.md - fix example code

gradle does not expand variables if the string has single quotes

Closes #37516
https://github.com/dart-lang/sdk/pull/37516

GitOrigin-RevId: ec4cfb0e7cf56d9ec5eb613ce56d553cf44e9bb6
Change-Id: I07eb51bfdbd6a32f2739d2ff7a0882280aec40a5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108941
Reviewed-by: Samir Jindel <sjindel@google.com>
Commit-Queue: Samir Jindel <sjindel@google.com>

samples/ffi/sqlite/docs/android.md

@@ -41,7 +41,7 @@ android {
     // ...
     sourceSets {
         main {
-            jniLibs.srcDir '${project.projectDir.path}/../../native-libraries'
+            jniLibs.srcDir "${project.projectDir.path}/../../native-libraries"
         }
     }
 }