Fix dependabot test-dependencies group io.mockk regex (flutter#8406)

After flutter#8100,  flutter/packages#8358 and flutter/packages#8357 should have been grouped into one dependabot PR to bump io.mockk:mockk to 1.13.14 across all packages.  Fix the regex to match `io.mockk:mockk`.

Author: jmagman

.github/dependabot.yml

@@ -109,7 +109,7 @@ updates:
       test-dependencies:
         patterns:
           - "androidx.test:*"
-          - "io.mockk:mockk:*"
+          - "io.mockk:*"
           - "junit:junit"
           - "org.mockito:*"
           - "org.robolectric:*"