[android] Remove XFAIL for tests that started passing.

These tests were disabled in swiftlang#33500 (a0333a4) and swiftlang#30390
(6ac04c6) because the optimizer did not seem to be working in
Android ARMv7.

At some moment between October 21st and October 30th something unbroke
the tests. I have looked into the changes in the SILOptimizer directory,
but I cannot pinpoint it to any of them in particular. It might be also
changes introduced in LLVM.

Author: drodriguez

test/SILOptimizer/let_properties_opts.swift

@@ -3,9 +3,6 @@
 
 // REQUIRES: optimized_stdlib
 
-// See https://bugs.swift.org/browse/SR-12370
-// XFAIL: OS=linux-androideabi && CPU=armv7
-
 // Test propagation of non-static let properties with compile-time constant values.
 
 // TODO: Once this optimization can remove the propagated fileprivate/internal let properties or

test/SILOptimizer/opt-remark-generator.swift

@@ -1,8 +1,6 @@
 // RUN: %target-swiftc_driver -O -Rpass-missed=sil-opt-remark-gen -Xllvm -sil-disable-pass=FunctionSignatureOpts -emit-sil %s -o /dev/null -Xfrontend -verify
 // REQUIRES: optimized_stdlib,swift_stdlib_no_asserts
 
-// XFAIL: OS=linux-androideabi && CPU=armv7
-
 public class Klass {}
 
 // TODO: Change global related code to be implicit/autogenerated (as