GPTQ Env vars: catch correct type of error (#596)

# What does this PR do?

When passing in environment variables like gptq_bits, we still get
errors thrown from TGI because the try/catch block is catching the wrong
type of error. This PR aims to fix that.

@Narsil - let me know if this is how you want this formatted. My Python
is a little shaky, so I hope this syntax is correct.

server/text_generation_server/utils/weights.py

@@ -130,7 +130,7 @@ class Weights:
             try:
                 bits = self.get_tensor("gptq_bits").item()
                 groupsize = self.get_tensor("gptq_groupsize").item()
-            except SafetensorError as e:
+            except (SafetensorError, RuntimeError) as e:
                 try:
                     import os
 
@@ -159,7 +159,7 @@ class Weights:
             try:
                 bits = self.get_tensor("gptq_bits").item()
                 groupsize = self.get_tensor("gptq_groupsize").item()
-            except SafetensorError as e:
+            except (SafetensorError, RuntimeError) as e:
                 try:
                     import os