Update cheatsheets

tldr/pgmcrater

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# pgmcrater
+
+> This command is superseded by `pamcrater`, `pamshadedrelief`, and `pamtopnm`.
+> More information: <https://netpbm.sourceforge.net/doc/pgmcrater.html>.
+
+- View documentation for `pamcrater`:
+
+`tldr pamcrater`
+
+- View documentation for `pamshadedrelief`:
+
+`tldr pamshadedrelief`
+
+- View documentation for `pamtopnm`:
+
+`tldr pamtopnm`