core: remove unnecessary #include <osmocom/core/talloc.h>

Including this header just for TALLOC_CTX is an overkill, we use
'void *' for talloc contexts in nearly all other Osmocom projects.

Change-Id: I4b9ffd7a329081df3d2c0b0ee8698a3cf759e94e
Related: OS#5960
diff --git a/src/core/bitvec.c b/src/core/bitvec.c
index 350f738..38ea1bb 100644
--- a/src/core/bitvec.c
+++ b/src/core/bitvec.c
@@ -395,7 +395,7 @@
  *  \param[in] size Number of bytes in the vector
  *  \param[in] ctx Context from which to allocate
  *  \return pointer to allocated vector; NULL in case of error */
-struct bitvec *bitvec_alloc(unsigned int size, TALLOC_CTX *ctx)
+struct bitvec *bitvec_alloc(unsigned int size, void *ctx)
 {
 	struct bitvec *bv = talloc(ctx, struct bitvec);
 	if (!bv)