Update opentelemetry-specification version to v1.38.0 (#5375)

Author: opentelemetrybot

.gitmodules

@@ -7,7 +7,7 @@
 [submodule "content-modules/opentelemetry-specification"]
 	path = content-modules/opentelemetry-specification
 	url = https://github.com/open-telemetry/opentelemetry-specification.git
-	spec-pin = v1.37.0
+	spec-pin = v1.38.0
 [submodule "content-modules/community"]
 	path = content-modules/community
 	url = https://github.com/open-telemetry/community

content-modules/opentelemetry-specification

@@ -18,7 +18,7 @@
 my $semConvRef = "$otelSpecRepoUrl/blob/main/semantic_conventions/README.md";
 my $specBasePath = '/docs/specs';
 my %versions = qw(
-  spec: 1.37.0
+  spec: 1.38.0
   otlp: 1.3.2
   semconv: 1.28.0
 );