Move some error flags to warnings

Appears to be a GCC bug causing `restrict` warnings, and some
`maybe-uninitialized` ones that are more senstive.  Downgrade them to
warnings since getting the compiler upgraded is time-sensitive.

Signed-off-by: Samuel E. Browne <[email protected]>

Author: sebrowne

cmake/ProjectCompilerPostConfig.cmake

@@ -67,7 +67,9 @@ set(upcoming_warnings
     dangling-pointer=2  # -Wall
     # deprecated-copy  # -Wextra, lots of warnings
     implicit-fallthrough=3  # -Wextra
+    maybe-uninitialized
     pessimizing-move  # -Wall
+    restrict
     #unused-parameter  # -Wextra, lots of warnings
     ${Trilinos_ADDITIONAL_WARNINGS}
 )
@@ -118,7 +120,6 @@ set(promoted_warnings
     int-to-pointer-cast
     logical-not-parentheses
     main
-    maybe-uninitialized
     memset-elt-size
     memset-transposed-args
     misleading-indentation
@@ -138,7 +139,6 @@ set(promoted_warnings
     range-loop-construct
     redundant-move  # -Wextra
     reorder
-    restrict
     return-type
     self-move
     sequence-point