Tweak AbstractMatcherTestChecker

Refaster template parameters will never match only the identifier of a
method's receiver parameter, so for the purpose of testing `@Matches`
and `@NotMatches` predicate classes, there's no need to descend into
`VariableTree#getNameExpression()`.

See https://docs.oracle.com/javase/specs/jls/se21/html/jls-8.html#jls-8.4

Author: Stephan202

refaster-support/src/test/java/tech/picnic/errorprone/refaster/matchers/AbstractMatcherTestChecker.java

@@ -84,7 +84,6 @@ public Description matchCompilationUnit(CompilationUnitTree compilationUnit, Vis
          * variable declaration. While the latter can be `ExpressionTree`s, they will never be
          * matched by Refaster.
          */
-        scan(tree.getNameExpression(), null);
         scan(tree.getInitializer(), null);
         return null;
       }