Fixes #24233: Remove misleading JDK compatibility hint for TASTy errors (#25171)

Fix misleading JDK compatibility error message for TASTy version
mismatches
Fixes #24233

### Description
When the compiler encounters a TASTy version mismatch (e.g., attempting
to read a TASTy file produced by a newer compiler version like 3.7.1
with compiler 3.3.6), it throws an `UnpickleException`. The error
handling code in _`ClassfileParser`_ and `ClassfileTastyUUIDParser `was
catching this as a generic `RuntimeException `and appending a misleading
message suggesting to "check the JDK compatibility of your Scala
version."

### This message was confusing because:

The error is about TASTy format versions (majorVersion: 28), not Java
classfile versions
The JDK version suggestion is irrelevant to TASTy compatibility issues

### Changes Made

- Modified exception handlers in `ClassfileParser.scala` and
`ClassfileTastyUUIDParser.scala`
- Added pattern matching to detect `UnpickleException `specifically
- Suppress JDK compatibility hint for TASTy unpickling errors
- Preserve the hint for actual classfile version issues

### Example
**Before:**

```
class file ... is broken (version 52.0),
  please check the JDK compatibility of your Scala version (3.3.6),
  reading aborted with class dotty.tools.tasty.UnpickleException:
  TASTy signature has wrong version...
```

**After:**

```
class file ... is broken,
  reading aborted with class dotty.tools.tasty.UnpickleException:
  TASTy signature has wrong version...

```
The UnpickleException message already contains clear information about
the TASTy version mismatch, making the JDK hint unnecessary and
confusing.

Testing

- Manually verified code correctness through inspection
- Changes are minimal and focused on error message formatting
- No functional changes to compilation logic

Author: Bbn08

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -5,7 +5,7 @@ package classfile
 
 import scala.language.unsafeNulls
 
-import dotty.tools.tasty.{ TastyReader, TastyHeaderUnpickler }
+import dotty.tools.tasty.{ TastyReader, TastyHeaderUnpickler, UnpickleException }
 
 import Contexts.*, Symbols.*, Types.*, Names.*, StdNames.*, NameOps.*, Scopes.*, Decorators.*
 import SymDenotations.*, unpickleScala2.Scala2Unpickler.*, Constants.*, Annotations.*, util.Spans.*
@@ -306,7 +306,9 @@ class ClassfileParser(
   catch {
     case e: RuntimeException =>
       if (ctx.debug) e.printStackTrace()
-      val addendum = Header.Version.brokenVersionAddendum(classfileVersion)
+      val addendum = e match
+        case _: UnpickleException => ""
+        case _ => Header.Version.brokenVersionAddendum(classfileVersion)
       throw new IOException(
         i"""  class file ${classfile.canonicalPath} is broken$addendum,
           |  reading aborted with ${e.getClass}:

compiler/src/dotty/tools/dotc/core/classfile/ClassfileTastyUUIDParser.scala

@@ -12,7 +12,7 @@ import dotty.tools.dotc.core.Symbols.*
 import dotty.tools.dotc.core.Types.*
 import dotty.tools.dotc.util.*
 import dotty.tools.io.AbstractFile
-import dotty.tools.tasty.TastyReader
+import dotty.tools.tasty.{ TastyReader, UnpickleException }
 
 import ClassfileParser.Header
 
@@ -37,7 +37,9 @@ class ClassfileTastyUUIDParser(classfile: AbstractFile)(ictx: Context) {
   catch {
     case e: RuntimeException =>
       if (ctx.debug) e.printStackTrace()
-      val addendum = Header.Version.brokenVersionAddendum(classfileVersion)
+      val addendum = e match
+        case _: UnpickleException => ""
+        case _ => Header.Version.brokenVersionAddendum(classfileVersion)
       throw new IOException(
         i"""  class file ${classfile.canonicalPath} is broken$addendum,
           |  reading aborted with ${e.getClass}: