bug KnpLabs#890 Fix broken roave/bc-check test (acrobat)

This PR was merged into the 2.x branch.

Discussion
----------

Previously the bc-check was broken due to a changed tag format, which causes an incorrect version/tag to be guessed. This was fixed in 5.0

```
Detected last minor version: 2.14.0

In Process.php line 256:

  The command "'git' 'rev-parse' '2.14.0'" failed.

  Exit Code: 128(Invalid exit argument)


  Output:
  ================
  2.14.0


  Error Output:
  ================
  fatal: ambiguous argument '2.14.0': unknown revision or path not in the working tree.
  Use '--' to separate paths from revisions, like this:
```



Commits
-------

88e7a23 Fix broken roave/bc-check test

Author: acrobat

.github/bc-test.sh

@@ -18,9 +18,9 @@ php:
 
 matrix:
   include:
-    - php: 7.2
+    - php: 7.4.7
       name: Backward compatibillity check
-      env: DEPENDENCIES="roave/backward-compatibility-check" TEST_COMMAND="./.github/bc-test.sh"
+      env: DEPENDENCIES="roave/backward-compatibility-check" TEST_COMMAND="vendor/bin/roave-backward-compatibility-check"
     - php: 7.1
       name: phpstan
       script: