Actions: Fix some Ql4Ql violations.

[michaelnebel]

Fix some Ql4Ql violations based on the following checks

• ql/field-only-used-in-charpred
• ql/could-be-cast
• ql/counting-to-zero
• ql/dataflow-module-naming-convention
• ql/if-with-none
• ql/missing-parameter-qldoc
• ql/misspelling

DCA looks good.

[Copilot]

Pull Request Overview

This PR fixes Ql4Ql violations across various security-related query files in the GitHub Actions CodeQL library. The changes primarily address code quality issues by removing unused variables, simplifying conditional logic, and correcting minor documentation issues.

• Eliminates unused variables in class constructors and predicates
• Simplifies conditional logic patterns using exists clauses instead of if-then-else constructs
• Fixes a spelling error in documentation

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
ArtifactPoisoningPathTraversal.ql	Refactors upload artifact check to use instanceof instead of exists
UseOfUnversionedImmutableAction.qll	Removes unused immutable_action field
OutputClobberingQuery.qll	Removes unused variables and moves them to exists scope
EnvVarInjectionQuery.qll	Moves unused variables to exists scope in class constructors
ControlChecks.qll	Moves unused condition variable to exists scope
ArtifactPoisoningQuery.qll	Removes unused variables and refactors if-then-else to conditional logic
ArgumentInjectionQuery.qll	Removes unused argument variables
FlowSources.qll	Moves unused variables to exists scope
ExternalFlow.qll	Refactors if-then-else to conditional logic
BasicBlocks.qll	Fixes typo in comment from bb to bbStart
Ast.qll	Refactors if-then-else constructs and fixes spelling error
Locations.qll	Updates parameter names in documentation comment