Remove SystemProperty from FlowSources

Author: JLLeitschuh

java/ql/lib/semmle/code/java/dataflow/FlowSources.qll

@@ -6,7 +6,6 @@ import java
 import semmle.code.java.dataflow.DataFlow
 import semmle.code.java.dataflow.TaintTracking
 import semmle.code.java.dataflow.DefUse
-import semmle.code.java.environment.SystemProperty
 import semmle.code.java.frameworks.Jdbc
 import semmle.code.java.frameworks.Networking
 import semmle.code.java.frameworks.Properties
@@ -183,8 +182,6 @@ class EnvInput extends LocalUserInput {
     // Results from various specific methods.
     this.asExpr().(MethodAccess).getMethod() instanceof EnvReadMethod
     or
-    this.asExpr() = getSystemProperty(_)
-    or
     // Access to `System.in`.
     exists(Field f | this.asExpr() = f.getAnAccess() | f instanceof SystemIn)
     or