Back out concrete SIMD floating-point inits for now.

I had hoped that #54445 would unblock these, but it doesn't seem to quite be the complete story yet (or at least, these were still failing as implemented).

Author: stephentyrone

stdlib/public/core/SIMDFloatConcreteOperations.swift.gyb

@@ -34,6 +34,8 @@ extension SIMD${n} where Scalar == ${Scalar} {
     _storage = ${Scalar}.SIMD${storageN}Storage(_builtin)
   }
 
+  /* Breaks differentiation testing, commented out while we figure out
+     what to do about that.
   @_alwaysEmitIntoClient @_transparent
   public init(repeating scalar: ${Scalar}) {
     let asVector = Builtin.insertelement_${Builtin}_FPIEEE${bits}_Int32(
@@ -50,6 +52,7 @@ extension SIMD${n} where Scalar == ${Scalar} {
     ))
 %end
   }
+  */
 
 %  if n >= 4:
   @_alwaysEmitIntoClient @_transparent

test/stdlib/SIMDFloatInitializers.swift.gyb

@@ -14,6 +14,10 @@
 // RUN: %target-swift-frontend -primary-file %t/SIMDFloatInitializers.swift -S | %FileCheck %t/SIMDFloatInitializers.swift --check-prefix=CHECK --check-prefix=CHECK-%target-cpu --check-prefix=CHECKOnone-%target-cpu
 // RUN: %target-swift-frontend -primary-file %t/SIMDFloatInitializers.swift -S -O | %FileCheck %t/SIMDFloatInitializers.swift --check-prefix=CHECK --check-prefix=CHECK-%target-cpu --check-prefix=CHECKO-%target-cpu
 
+// Disable this test for now because aEIC/transparent functions still are not
+// correctly differentiable, and so these inits are suppressed in the stdlib.
+// REQUIRES: differentiable-aEIC-transparent
+
 import Swift
 
 %for bits in [16,32,64]: