Remove incorrect assumption
Remove incorrect assumption

Now that we have implicit field reads, it is no longer the case
that the base of a field read instruction will be an eval
instruction.

github/codeql,github/codeql,github/codeql,github/codeql,github/codeql-go,github/codeql,github/codeql-go,github/codeql,github/codeql,github/codeql-go,github/codeql,github/codeql,github/codeql,github/codeql-go,github/codeql,github/codeql,github/codeql,github/codeql,github/codeql