Update severity and precision of a few injection queries

These will wind up in `security-extended`, when previously they were not in any of the standard suites.

actions/ql/src/Security/CWE-077/EnvPathInjectionMedium.ql

@@ -2,9 +2,9 @@
  * @name PATH Enviroment Variable built from user-controlled sources
  * @description Building the PATH environment variable from user-controlled sources may alter the execution of following system commands
  * @kind path-problem
- * @problem.severity warning
+ * @problem.severity error
  * @security-severity 5.0
- * @precision high
+ * @precision medium
  * @id actions/envpath-injection/medium
  * @tags actions
  *       security

actions/ql/src/Security/CWE-077/EnvVarInjectionMedium.ql

@@ -2,9 +2,9 @@
  * @name Enviroment Variable built from user-controlled sources
  * @description Building an environment variable from user-controlled sources may alter the execution of following system commands
  * @kind path-problem
- * @problem.severity warning
+ * @problem.severity error
  * @security-severity 5.0
- * @precision high
+ * @precision medium
  * @id actions/envvar-injection/medium
  * @tags actions
  *       security

actions/ql/src/Security/CWE-829/ArtifactPoisoningMedium.ql

@@ -2,8 +2,8 @@
  * @name Artifact poisoning
  * @description An attacker may be able to poison the workflow's artifacts and influence on consequent steps.
  * @kind path-problem
- * @problem.severity warning
- * @precision high
+ * @problem.severity error
+ * @precision medium
  * @security-severity 5.0
  * @id actions/artifact-poisoning/medium
  * @tags actions