fix: address review — guard OSS_VERSION + modern conda activate

- Add guard to fail early if OSS_VERSION is empty instead of
  silently writing empty version into build.sbt
- Replace deprecated 'source activate' with modern conda syntax
  (eval conda shell.bash hook + conda activate) in all 4 occurrences

Co-authored-by: Samhitha Mamindla <smamindla@microsoft.com>

Author: smamindl

pipeline.yaml

@@ -844,6 +844,7 @@ jobs:
         cd $(Build.SourcesDirectory)/SynapseML-Internal
 
         echo "=== Retargeting Internal to OSS version $(OSS_VERSION) ==="
+        [ -n "$(OSS_VERSION)" ] || { echo "##vso[task.logissue type=error]OSS_VERSION is not set"; exit 1; }
         sed -i 's|val synapseMLVersion = ".*"|val synapseMLVersion = "$(OSS_VERSION)"|' build.sbt
         sed -i '/^resolvers ++= Seq(/a\  Resolver.mavenLocal,' build.sbt
 
@@ -914,7 +915,8 @@ jobs:
         inlineScript: |
           set -e
           cd $(Build.SourcesDirectory)/SynapseML-Internal
-          source activate synapseml-internal
+          eval "$(conda shell.bash hook)"
+          conda activate synapseml-internal
           export CREATE_SEMPY_WRITER=false
           export SBT_OPTS="-Xmx4G -Xss2M -Duser.timezone=GMT"
           echo "Running Internal tests against OSS $(OSS_VERSION)..."
@@ -944,7 +946,8 @@ jobs:
         inlineScript: |
           set -e
           cd $(Build.SourcesDirectory)/SynapseML-Internal
-          source activate synapseml-internal
+          eval "$(conda shell.bash hook)"
+          conda activate synapseml-internal
           export CREATE_SEMPY_WRITER=false
           export SBT_OPTS="-Xmx4G -Xss2M -Duser.timezone=GMT"
           echo "Packaging Internal Python against OSS $(OSS_VERSION)..."
@@ -961,7 +964,8 @@ jobs:
         inlineScript: |
           set -e
           cd $(Build.SourcesDirectory)/SynapseML-Internal
-          source activate synapseml-internal
+          eval "$(conda shell.bash hook)"
+          conda activate synapseml-internal
           export CREATE_SEMPY_WRITER=false
           export SBT_OPTS="-Xmx4G -Xss2M -Duser.timezone=GMT"
           echo "Running Internal Python tests against OSS $(OSS_VERSION)..."
@@ -988,7 +992,8 @@ jobs:
         inlineScript: |
           set -e
           cd $(Build.SourcesDirectory)/SynapseML-Internal
-          source activate synapseml-internal
+          eval "$(conda shell.bash hook)"
+          conda activate synapseml-internal
           export CREATE_SEMPY_WRITER=false
           export SBT_OPTS="-Xmx4G -Xss2M -Duser.timezone=GMT"
           echo "Creating MLflow model fixtures..."