expressionsem: Remove redundant dependency to dmd.root.file (#15083)

FileManager.lookup will already attempt to read the file if it is not cached,
and will insert it in the list of files if it manages to read it,
so only the 'if (!readResult.success)' branch was reachable.
This in turn allows us to remove expressionsem's dependency
to dmd.root.file.

compiler/src/dmd/expressionsem.d

@@ -65,7 +65,6 @@ import dmd.parse;
 import dmd.printast;
 import dmd.root.array;
 import dmd.root.ctfloat;
-import dmd.root.file;
 import dmd.root.filename;
 import dmd.common.outbuffer;
 import dmd.root.rootobject;
@@ -6318,19 +6317,8 @@ private extern (C++) final class ExpressionSemanticVisitor : Visitor
             }
             else
             {
-                auto readResult = File.read(resolvedNamez);
-                if (!readResult.success)
-                {
-                    e.error("cannot read file `%s`", resolvedNamez.ptr);
-                    return setError();
-                }
-                else
-                {
-                    // take ownership of buffer (probably leaking)
-                    auto data = readResult.extractSlice();
-                    se = new StringExp(e.loc, data);
-                    global.fileManager.add(fileName, data);
-                }
+                e.error("cannot read file `%s`", resolvedNamez.ptr);
+                return setError();
             }
         }
         result = se.expressionSemantic(sc);