fix: add missing pp-spaces in grind_pattern

[adomani]

This PR adds a pretty-printed space in grind_pattern.

#lean4 > Some pretty printing quirks @ 💬

[leanprover-community-bot]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 949cf6924649a3ad3aa934ee4466438bd6994064 --onto 6a0b0c8273ab560d093494a2daa4dd3088437ad1. You can force Mathlib CI using the force-mathlib-ci label. (2025-12-15 18:19:44)
• ❗ Mathlib CI can not be attempted yet, as the nightly-testing-2025-12-23 tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto nightly-with-mathlib, Mathlib CI should run now. You can force Mathlib CI using the force-mathlib-ci label. (2025-12-23 11:26:59)

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase 949cf6924649a3ad3aa934ee4466438bd6994064 --onto 646df6ba16b3f68de539a085456c323e160e206d. You can force reference manual CI using the force-manual-ci label. (2025-12-15 18:19:45)
• ❗ Reference manual CI can not be attempted yet, as the nightly-testing-2025-12-23 tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto nightly-with-manual, reference manual CI should run now. You can force reference manual CI using the force-manual-ci label. (2025-12-23 11:27:01)

[grunweg]

Seems sensible to me, thanks!